RE: Friday 13 and Friday 13
Richard Mallett wrote: Just to clarify : The answer to the original question is that this situation recurs every 28 years, so will have occurred in 1987, 1959, 1931, 1903 and 1874 (29 years because 1900 was not a leap year) and will occur again in 2043, 2071, 2099 and 2128 (29 years because 2100 will not be a leap year) Although the situation does usually recur every 28 years, I do not think this is the complete answer, nor that it will occur in 2128, as that is a leap year - when March 13 will fall on Saturday. We would guess that February 13th must be a Friday about one year in seven, or there would not be enough days of the week to go round; and that about one-quarter of these will be a leap year and March 13th will be Saturday. So: Three times in a 28 year cycle (an ordinary one, not including a century non-leap year) February 13 falls on Friday and the year is not leap, so March 13 is also Friday. The intervals are 6, 11, and 11 years, according to whether the start year is 1, 2, or 3 after a leap year, so that they include 1, 3, or 3 leap years. This works because 6+1 and 11+3 are both multiples of 7. The Friday 13th pair in February and March occurred in 1953, 1959, 1970, 1981, 1987, 1998 then 2009 (as 2000 was leap it did not disturb the 6, 11, 11 sequence). Then add 6 to give the present year, 2015, next add 11 and 11 to give 2026 and 2037, then 2043, 54, 65; 2071, 82, 93, 2099. However 2100 not being leap changes the sequence in this case to make three six-year intervals in a row, 2093, 2099, 2105, 2111, before settling back to 2122 and 2133 followed by 2139, 50, 61 ... The six year interval spanning the century includes just one leap year. The same happens around 2200 with 2189, 2195, 2201, 2207. But at 2300 (as happened at 1900) there is a twelve-year gap, including two leap years, in place of an eleven-year one including three: 2285, 2291, 2303, 2314, 2325, then 2331, 2342, 2353. Similarly 400 years earlier the sequence ran 1874, 1885, 1891, 1903, 1914. 2400 being leap means the 6, 11, 11 year interval sequence runs through it undisturbed, as happened at 2000. Regards, Andrew James Secure Meters (UK) Ltd. is a registered company in England: 2199653 Secure House, Moorside Road, Winchester, SO23 7RX This correspondence is confidential and solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Friday 13 and Friday 13
As there are 24 leap years in three out of four centuries and 25 in the fourth, in a 400 year period there are 303*365+97*366 = 146097 = 20871*7 days. So the weekday pattern repeats every 400 years, as this is exactly 20871 weeks. The relationship of weekdays to dates is such that the 13th of the month falls more often on Friday in the 400 year period than on any other day of the week - not a large bias, but one which doesn't go away! The 13th falls on Monday 685, Tuesday 685, Wednesday 687, Thursday 684, Friday 688, Saturday 684, and Sunday 687 times. Regards, Andrew James Secure Meters (UK) Ltd. is a registered company in England: 2199653 Secure House, Moorside Road, Winchester, SO23 7RX This correspondence is confidential and solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: SCOTTISH SUNDIAL
I remember seeing that pattern at Ottery St Mary and Alton and perhaps elsewhere but John has beaten me to it in mentioning that! It looked most probably early 20th century to me. I would say that the existence of several more or less identical such dials widely separated indicates more or less definitely that it's not genuine 1684, though my logic in that deduction may be a bit tenuous? Regards, Andrew James From: sundial [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Dennis Cowan Sent: 21 January 2014 21:39 To: sundial@uni-koeln.de Subject: SCOTTISH SUNDIAL I wonder if anyone on the list can help? I received photos of this sundial from a lady in the USA. She aquired it whilst she lived in Scotland some twenty odd years ago. I'm trying to trace the possible origins for her. I am not sure if the date of 1684 is genuine as it looks quite fresh, but a reproduction would surely use a known motto and I have never heard of this one Ye Shade Teecheth. The compass is also unusual to me. Does anyone have any opinions? Is it original or a reproduction.? Does anyone recognise the motto or style of compass? Many thanks Dennis Cowan This message has been scanned for viruses by MailControlhttp://www.mailcontrol.com/. Secure Meters (UK) Ltd. is a registered company in England: 2199653 Secure House, Moorside Road, Winchester, SO23 7RX This correspondence is confidential and solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: azimuth lines
The Queens' College dial certainly has azimuth lines as John wrote. Frank, is it possible that some feature of the rather nice ornamental and unusual gnomon support provides the nodus? Working from the azimuth line spacing you should be able to estimate the required height of the nodus and see whether this is at all plausible. The 8 support looks too low down the dial really, but it may be worth a calculation if only to rule it out! Regards Andrew James Secure Meters (UK) Ltd. is a registered company in England: 2199653 Secure House, Moorside Road, Winchester, SO23 7RX This correspondence is confidential and solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: St. Margareth
Dear Reinhold, Thank you for sharing that link http://www.cadrans-solaires.fr/cadrans-Londres-saint-margareth.html http://www.cadrans-solaires.fr/cadrans-Londres-saint-margareth.html and that picture of the fine St Margaret's, Westminster sundials. I believe they were designed by Chris Daniel and made by Brookbrae but am open to correction. Something about them which has always caused me to wonder is the absence of hours from about 6 to 8 a.m. and 4 to 6 p.m. on the North dial, which only shows hours before 6 a.m. and after 6 p.m. - not the whole time the Sun is to the North at midsummer. I can think of at least two possible reasons: - firstly, having the gnomon planted as it is in the ring, and near the edge, would make the space for them insignificantly small. - secondly, the projecting corner turrets of the church tower probably shade the dial until the Sun is some way North of due East or due West. The North gnomon could have been designed differently but would then be less like an inverted version of the South gnomon and this would reduce the overall symmetry. Of course, having also East and West dials means there is no shortage of somewhere to read the time during these hours. Can anyone comment on this? Regards Andrew James Secure Meters (UK) Ltd. is a registered company in England: 2199653 Secure House, Moorside Road, Winchester, SO23 7RX This correspondence is confidential and solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: sundials and tower clocks
Dear John, Frank, Kevin, et al, I remember a letter from Charles Aked in Antiquarian Horology circa 1970 showing his son (then about 8?) at one of the Scottish lighthouse dials in situ. I believe they were all (?) sold off perhaps about 15 years ago and think I have a cutting somewhere from a newspaper article showing them in a sort of well ordered heap. Regarding the Tompion dial at the Pump Room, a letter in Horological Journal in I think March 1960 shows what is probably this dial, so actually it was discovered by that writer near Bath some years before Brigadier Neilson found it and presented it to the Pump Room. Regards Andrew James This message has been scanned for viruses by MailControl http://www.mailcontrol.com/ . Secure Meters (UK) Ltd. is a registered company in England: 2199653 Secure House, Moorside Road, Winchester, SO23 7RX This correspondence is confidential and solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Prague Clock
-Original Message- Frank King wrote: ... Or have I missed something crucial? [It is still a splendid clock, but I want to be clear about its design limitations!] -- I think we must remember that the timekeeping mechanism driving the astronomical or astrolabic gearing of the Prague clock is mid 19th century (and it is itself very interesting - I was privileged to visit the insides of the clock some years ago). By that time, a clock mechanism kept pretty accurate mean time, so that, once regulated, its accumulated error from mean time would not be noticeable for many days, especially on a 24-hour dial. However its original predecessor(s) - 1410 and later - would have been very poor at public timekeeping by our standards, with random errors of the order of several minutes or tens of minutes per day. Hence it would need regular correction; and the only instrument conveniently telling the true time to which to correct it was a sundial. So it *automatically* would be regulated to - and keep - (local) solar time without any need to compute the equation of time - which although known about by scholars was then not even tabulated as we know it. Sir George White gave a most interesting lecture a few years ago expounding the proposition that the English lantern clock in the early 17th century - a very poor timekeeper by modern standards - was in fact excellently suited to keeping practical time from day to day (and overnight), which anyway needed to be adjusted to stay in line with local solar time, as that was then the only standard. Fortuitously the time zone GMT+1 is fairly close to local mean time for the Prague clock as it is at 14d 25m East - so the discrepancy is about 2 minutes 19 seconds. It would be far worse off in Seville! So I suggest that: - originally the Prague clock certainly kept local solar time, being frequently adjusted (corrected) to that from its own (very) approximate timekeeping: - when the local time standard become mean rather than solar it would have still been frequently adjusted of necessity, but I do not myself know whether to mean or solar time, nor do I know when mean time was adopted in Prague: - after the mid-19th century work it would naturally keep mean time quite well but could have been adjusted to local solar time if desired: - after the adoption of time zones it may or may not have been adjusted to civil time: - and now it is adjusted to CET (UTC+1). I suspect the convenience and motivation for keeping civil time is mostly so that tourists know when to expect the automata to perform, rather than because viewers will use it to set their watches. Andrew James Secure Meters (UK) Ltd. is a registered company in England: 2199653 Secure House, Moorside Road, Winchester, SO23 7RX This correspondence is confidential and solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
BSS web site
Dear all I thought the British Sundial Society web site was at http://www.sundialsoc.org.uk/ - but it seems to have been hijacked to sell lawnmowers and such like! What is going on? Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 Measure - Inform - Empower This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Evelyn Fox Court sundial
Today's Guardian, I am told, has on page 37 an obituary of architect Sam Lloyd featuring an illustration of one of his buildings, I think Evelyn Fox Court, in North Kensington, London, which has what looks like a sundial on its wall. Unfortunately the on-line version at http://www.guardian.co.uk/artanddesign/2009/oct/14/sam-lloyd-obituary does not have this picture. Does anyone know anything about this dial? Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 Measure - Inform - Empower This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Equinox and Equatorial Rings
John Foad asked: are there any programs that will give the truer line? One problem presumably is that the lines are different according to whether the solar declination is increasing or decreasing, so there are two for every value of declination (except - more or less - at the solstices), making a rather confused appearance - I guess there would probably in effect be a thickening of the double ends of the lines compared with the middle? Regards, Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 Measure - Inform - Empower This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Dutch sundial
John Davis asked: Preteritum Nihil, Præsens Instabile, Futurum Incertum (The past is gone, the present transient, the future uncertain) Where does it come from? Nicolas Reusner said something fairly similar in one of his Epigrams, writing about the Fates: Praesens instabile est (sic Sors rotat omnia terra) Praeteritum nihil amplius: incertumque futurum which means something like: The present is transient (thus does Fate spin the whole earth); the past is no more; and the future uncertain The text (in a 1593 edition of his works) can be seen at http://www.uni-mannheim.de/mateo/camena/reus2/jpg/reus499.jpg I don't know whether there is an earlier version of the same sentiment, which he may have had in mind; perhaps someone can point to an instance from Classical times, or cite an earlier author? Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 Measure - Inform - Empower This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Google Method of Finding Declination
Re Damia Soler's Sundial Location Calculator - what a great tool! One small point - if I put in a UK postcode for the address, the resulting satellite picture seems to be a little way (a mile or so?) away, whereas normally the location found by Google maps is more or less exactly correct (at least where the postcode covers a small area as in a town). Secondly, does anyone know how accurate (in the UK) the lat/long figures this technique gives are? How does the uncertainty relate to say a minute or a second of longitude or latitude? Does anyone have some clearly identifiable locations around the country with very accurately known positions on which one could check this? Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 Measure - Inform - Empower This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Chinese time - following The End of the Day
I found Mario's explanations on Roman and European hour systems most fascinating: thank you. I have a tangentially related question or questions; Mario mentioned that different times were appropriate to different people (country or city dwellers, perhaps). I understand (largely from Heavenly Clockwork by Needham et al.) that the Chinese may also have inherited their system of equal hours from the Babylonians. Like the Romans, the Chinese reckoned the boundary of the day at midnight. Some centuries BC the Chinese were using unequal hours, but around 200 BC their double hour system was perfected and became the only one for official use. In this, twelve equal double hour periods are named during the day (nychthemeron). Each has two halves and so each half is equal to one of our modern hours. The midpoint of one of these double hours was midnight, so the double hours straddle our times of , 0200, 0400, 0600 ... 2200 and the boundaries between them are at 0100, 0300, 0500 ... 2300. However, a system of unequal hour night watches continued alongside the use of equal double hours until the 19th century. So: Were unequal daytime hours also used for everyday purposes, as opposed to official ones, during this 2000 year period (from around 200 BC onwards)? I am not familiar with Chinese sundials but the only old ones I recall are equatorial and clearly appropriate for official use. I imagine that they are marked for equal (double) hours. Is this correct? Were there also - or are there still existing - old Chinese sundials which show unequal daytime hours, or were equal hours the only time shown? Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 Measure - Inform - Empower This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Moondial, rather than sundial, timekeeping related
I notice from the US Naval Observatory figures (http://aa.usno.navy.mil/data/docs/MoonPhase.php) that next year full moon occurs on the 2nd November 2009 at 19:14 GMT and new moon exactly (within a minute) 14 days later, 19:14 on the 16th November. On average I expect the interval to be half a lunation (29 d 12 h 44 m 3 s) or about 14 days 18 hours 22 minutes. The time from the October 18th new moon at 05:33 to November full is 15 days 13 h 41 m, 19 h 19 m longer than average I had not appreciated just how irregular the moon's motion was until I noticed this coincidence of times, 19:14 repeated. The inaccuracy of moondials becomes more apparent! How often does one see this 14 day interval? How often does it vary even more from the average? What are the extremes? Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 Measure - Inform - Empower This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Nun Appleton Dial Mystery
John Carmichael wrote: It no longer is there [Nun Appleton Hall] and I don't know when it was removed. It now resides in lightbox for display at entrance to York Art Gallery. And p.s. Do they allow people to visit that vestibule area? Last time I was in York (August 2007) it was no longer on display where I had previously (at the BSS York conference) seen it in the vestibule, which had been re-arranged, but had as I understood been taken into store. A pity - though I think it can still be seen on application in advance to the gallery. Regards Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 Measure - Inform - Empower This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Advice wanted, on 'Analemmatic' sundial orientation
Dear Alison, I think the experts have already told you what you need to know. Of course, re-aligning the drive to run North-South would help a little. This should be easier for Mr Phillips than re-aligning the Earth's axis. Placing the whole estate on a turntable would be an alternative allowing the present alignment of drive relative to house to be undisturbed. A rough and ready allowance for Summer Time could then be made twice a year which could become another tourist attraction if you can cope with having Summer and Winter entrances. You may not want to transport it to the Southern Hemisphere, though - nor to the pole when you can indeed use a semicircle (or better still, a full circle). Others may like to comment on the following thoughts: If, instead of standing on the central month scale, the user finds and stands on or near the hour number which casts his shadow onto the appropriate date, the numbers might be arranged to the South rather than to the North of the centre. This requires more action on the part of the user. A circular or other shape rather than a narrow rectangular centre bearing the date scale might disguise the alignment a little. If the hours were not in a horizontal plane, perhaps they could be arranged to lie on a semicircle in some other plane - though not, I think, what Mr Phillips would like? (I was once involved in rectifying, as far as possible given what was immovably fixed, an analemmatic dial at first incorrectly laid out, so I do wish you well in this endeavour. It still ended up having timekeeping errors but it was possible to spread them around so that none were too enormous.) Andrew James -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Alison Shields Sent: 03 June 2008 18:57 To: sundial@uni-koeln.de Subject: Advice wanted, on 'Analemmatic' sundial orientation Dear Sundial Experts, I have recently joined this Mailing List, and hope that any members will be able to give me some assistance on the following situation. Our local Stately Home (Kentwell Hall, Long Melford, Suffolk) is considering installing an Analemmatic sundial, as a new interactive attraction for visitors - but we are getting 'conflicting' advice, on whether this 'Human Sundial' will work in the way we want it to. We have been in discussion with Modern Sunclocks (apparently the acknowledged 'experts' for these features), who have told us that its central scale of dates must be aligned North/South - plus that hour markers must be correctly positioned on an elliptical ring, and which would lie on the Northern side of that scale of dates. Photographs on their website ( www.sunclocks.com ) confirm this. However, our 'Director of Operations' (Mr Phillips) absolutely INSISTS that he wants the scale to run exactly parallel with our main driveway - on a compass bearing which is about 162 degrees from North, with the hour points placed on its Southern side. He also wants the hour points to form an exact semi-circle, and not be elliptical in shape. Mr Phillips refuses to accept that he cannot arbitrarily position the Human Sundial feature as he wishes, and says that it must be possible to create this so that it could then align with the existing layout of buildings/paths. Can anyone on this Mailing List tell me whether it is possible to install a Human Sundial to fit any existing orientations, (with appropriate re-calculation of its component parts) - or, if not, just confirm that it must be as Modern Sunclocks have told me. I can then show the 'weight of evidence' to Mr Phillips. Because Kentwell Hall is a well-known Stately Home (open to the public), we should not want to become a 'laughing stock' by installing a feature which does not work - despite Mr Phillips assurance that all types of sundial can be adjusted to work, in any location. Looking forward to all comments (to this List, or sent privately). Sincerely, Alison Shields. --- https://lists.uni-koeln.de/mailman/listinfo/sundial This message has been scanned for viruses by MailControl PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 Measure - Inform - Empower This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Astronomical Clocks
Peter, You could of course buy a modern wrist-watch featuring equation of time and using a similar 'kidney' cam ... Blancpain and Audemars and perhaps others make them, but the Diallist's Companion is considerably cheaper! Andrew James -Original Message- On Behalf Of Peter Mayer Sent: 09 April 2008 03:31 Subject: Re: Astronomical Clocks snip Amongst the many other things which were utterly unknown to me were 18th century clocks which incorporated Equation of Time 'kidneys' so that they could read sundial time! Is the Dialist's Companion the only contemporary equivalent? PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Dali sundial +
Bob, Wouldn't both water clocks and fire clocks (whether incense burners or graduated candles) have claims to have most moving parts - there would be more particles in the smoke than grains of sand in an hourglass, wouldn't there? Also, even for mechanical timekeepers, counting the moving parts could be subject to disagreement - in cases where many parts are made but assembled into moving constructs (such as separately inserted teeth in a wooden wheel, as in Eisinga's planetarium) do you count the assembly as lots, or one? Andrew James From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Robert Terwilliger Sent: 13 March 2008 23:40 To: 'Sundial Mailing List' Subject: Dali sundial + Some time ago someone posted a link to a painting by Salvador Dali that included a sundial. Could someone point me to it again? == Try this: == Since it has none, I suppose a sundial could be considered the timepiece with the least moving parts. What timepiece has the most moving parts? Bob This message has been scanned for viruses by MailControl http://www.mailcontrol.com/ . PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Porcelain Sundials
John Carmichael wrote Now here's a thought- All over England I saw the clock faces on all the churches have only TWO colors (either black and gold or blue and gold). This leads me to believe that these clock faces might be made of low temp baked paint enamels and not porcelain. Does anybody know exactly what the English clock faces are made of? Most (almost all) flat English church clock dials of the type John refers to are painted and gilded on a flat or convex ground. Others have a skeleton of cast iron which can be glazed though sometimes it is open or placed in front of the wall. The ground is sometimes wood in older clocks (when it hasn't been replaced by something else - though a surprising number survive from 17th and 18th centuries) or copper, and copper or cast iron (19th-20th centuries) in newer ones. Occasionally stone is used. The numerals when gold should be done with 23.5 or 24 carat gold leaf. Cast iron allows the minute spaces and hour numbers to be definitely as intended and little subject to the vagaries of the repainter and the contrast with white or opal glass makes a clear dial which can be illuminated (as in the Great Clock of Westminster, commonly called Big Ben). Modern dials (post 1960) are usually glass fibre and have sometimes (wrongly I think) been used to replace older church clock dials - and for new buildings (especially supermarket clock towers etc). I do recall seeing one enamel church clock dial in England but can't remember where - East Anglia perhaps? On the other hand clock dials on the Continent quite often have enamelled dials. Often these are made in sections, at least in France. I hope this is of interest. Are enamelled cast-iron baths relevant to this discussion (not that I know anything about them?) Andrew James 51 04' N 1 17' W PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: The Housewife's Trick
I think I remember hearing that one of the two horizontal dials at Erddig (near Wrexham, North Wales - the sundial nearer the house) was loose on its pedestal and that members of the Yorke family rotated it twice yearly during the twentieth century to allow for Summer Time. Can anyone confirm this? Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk PRI Limited is a company registered in England and Wales with company number 2199653 The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Sundials - in the right place - are the future
See http://makeashorterlink.com/?D30A6224D for a short comment having this title in today's Daily Telegraph, following the news of the All Souls' dial. Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Sundial 'poetry'
Tony Moss wrote: As I recall the last-straw stimulus to seek alternatives was something like: A sailor who slept in the sun ... I don't think that I ever inflicted this follow-up on the list but (unfortunately?) I have now been encouraged to do so: For that sailor had great erudition In the old sciatheric tradition, And could judge his degrees With the consummate ease Of a natural geometrician! Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s).If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Southern hemisphere heliochronometer?
Bill Gottesman wrote The answer is yes. I think it was called Homan's Heliochronometer, and was made in South Africa. ... Althugh William Homan worked professionally in South Africa (and filed patents from there) all the instruments by him that I've ever seen have a Glasgow address. Bill, have you come across one made in South Africa? I have seen one by him made (at 22 Renfrew Street Glasgow) for about 8 degrees North - probably Trincomalee. Not quite the Southern hemisphere, but pretty close! Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl -
RE: bridge dials
Greetings Frank and others I think I have reported Maud Heath's dial near Kellaways, East Tytherton, Wiltshire, to the Register and was not the first to do so. Is it SRN 0401 - I haven't got any info to hand? It's not quite on a bridge, for as far as I remember it is built (C17) on the usually dry land beside the road - Maud Heath's causeway. She was a widow who in 1474 left a gift to build this dry route to market. See http://www.yourguide.org.uk/chippenham/maud.html for example and http://www.northwiltslink.co.uk/html/maud_heath_-_north_wiltshire.html has a picture of the sundial. The Wilton/Ross dial is on a bridge definitely known as Wilton Bridge and I think is just in Wilton which is beside and the other side of the river Wye below Ross. The dial was moved across the bridge at some time in the 20th century so that now the other side of it is seen from the road. (In the past there has been some confusion between this Wilton and Wilton, Wiltshire, where there is a very worn polyhedral sundial in the market place having strong similarities with that at Moccas Court.) There is a picture at http://www.wyevalley.fsworld.co.uk/wilton%20bridge.htm where it is also said to be incorrectly set, but I can't vouch for that. Another picture at http://www.wyenot.com/news/2005-01-18-3.htm may relate to its being moved but again I'm not certain of its origin. Andrew James -Original Message- From: Frank Evans [mailto:[EMAIL PROTECTED] Sent: 30 May 2005 12:25 To: Sundial Subject: bridge dials Greetings fellow dialists, Thanks for kind responses to my enquiry about bridge dials. It seems that the supposition that they are uncommon is true. David Brown has added another possible in the cubical dial on Maud Heath's causeway in Wiltshire (is this dial to be found somewhere in the BSS Register?). It seems the Ross on Wye dial is actually in Wilton (to Patrick Powers: no, I have no further information, Patrick). snip -
RE: Latin scholars
x-charset windows-1256I think there are two very similar but slightly different mottos here using similar but distinct verbs Praetereo - go by, pass by (ae not oe I think) Pereo - perish, pass away, vanish The meaning is essentially the same - they [the hours] pass and are reckoned Perhaps a Latinist can comment on the relation between the two words? Also Eheu fugaces, labuntur anni - (labuntur not labantur I think) - derives from Horace, Odes 2 14, meaning something like Alas, the fleeting years slip away though in the original the proper name of the friend to whom it is addressed occurs twice in the middle of it (Postume, O Postumus). Another sundial connection: from Boswell's Life of Johnson: An instance at once of his pensive turn of mind, and his cheerfulness of temper, appeared in a little story which he himself told to Mr Langton, when they were walking in his garden: 'Here (said he,) I had put a handsome sun-dial, with this inscription, Eheu fugaces! which (speaking with a smile) was sadly verified, for by the next morning my dial had been carried off.' Andrew James -Original Message- From: Douglas Bateman [mailto:[EMAIL PROTECTED] Sent: 11 May 2005 19:43 To: Sundial List Subject: Latin scholars Assistance please. I have a motto in Latin that appears to have different translations. Which is correct? The motto is on a pair of vertical dials and Mrs Gatty (4th edition 1900) gives the following Prْtereunt: They pass by Imputantur: They are reckoned However, our respected editor, Dr Margaret Stanier gives the same(?) motto as Pereunt et Imputantur as (The hours) pass away and are set down to (our) charge Margaret, in her small book on Oxford Sundials, shows this motto on the dial at All Souls' College and says that it is a quote from Martial's Epigrammata. The mottos don't look the same, but given the scope for mis-copying, are they supposed to be the identical? Comments please, Doug PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl - /x-charset
RE: high dials
There is a moderate sized brass South facing sundial about 25 feet up at the top of a stair turret at Axbridge church, Somerset. I've always wondered how it was to be read - unless you could climb out onto the roof and peer over the edge. But it wouldn't be much use for setting the clock, either. Unless of course, following Mike Shaw's suggestion, horses were MUCH, MUCH bigger at the start of the 19th century - or perhaps the then Squire had a personal elephant with a really spectacular howdah? ;-) Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl -
RE: Sundial Cupolas
There is a modern (1990s?) cupola with a South sundial on it at South Warnborough, in Hampshire. I believe the owner originally intended to put a clock in as well but am not sure whether he ever did. I can think of a few other similar arrangements around the country - for example I think Goodwood House has a large 18th century sundial and clock in such a position. However I can't recall seeing a proper set of four dials so arranged. Do you count the Gate of Honour at Gonville and Caius College, Cambridge, with its six sundials, as a cupola? See http://www.cai.cam.ac.uk/map/cCourt.php for a good view. If you ground the weathervane, bear in mind that lightning conductors should be substantial, avoid sharp bends, and go to a very good earth indeed. Andrew James -Original Message- From: John Carmichael [mailto:[EMAIL PROTECTED] Sent: 19 March 2005 17:56 To: Sundial List Subject: Sundial Cupolas Hello All: I'm considering building or buying a four-sided painted wood cupola with a copper roof for the roof of a home. I'd like to put a sundial on each face of the cupola and then a neat weathervane on top. snip Have any of you ever seen a cupola or clock tower with sundials instead of clocks? John p.s. Do you think the copper weathervane will act like a lightning rod? Maybe it should be grounded? snip PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl -
RE: azimuth diagram
Frank, Have a look at BSS Bulletin 13(ii) and 13(iii) where I think Tony Belk discusses the Weir diagram - he may also have written or talked about it more recently if my memory serves me. Andrew James -Original Message- From: Frank Evans [mailto:[EMAIL PROTECTED] Sent: 03 February 2005 21:18 To: Sundial Subject: azimuth diagram Greetings fellow dialists, The other day I bought a copy of Weir's Azimuth Diagram. ... (2) Have I got all this right? Is anyone else familiar with Weir's diagram and has it been mentioned before in this sundial group? Frank 55N 1W PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl -
RE: A Sundial Drama in One Act
I believe that there is a rather large and splendid analemmatic noon mark a couple of years old high on a new building which could possibly be not a million millimetres from where you may or may not have been, Frank. I do hope that somebody manages to photograph it one day; when I first chanced to see it, on a beautifully sunny morning, I did not have a camera with me, but perhaps that was just as well as I now learn ;-) . Andrew James PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl -
RE: alignment - Saint Sulpice
I think perhaps the double use of the word meridian lies at the root of this confusion. From its antecedent word meridies - the middle of the day - we see how it means a line for determining time of noon and that is local noon wherever it may be situated, be it Saint Sulpice, Bologna, or Durham. The use of a particular line of longitude where the Sun is at its highest, noon, at the same time, as a base for measurement or prime meridian is another matter, for that could be done without reference to the Sun at all, for example with the required North - South line being established by the stars from any suitably equipped place - London, Paris, Rome, Palermo ... In this day and age perhaps The Da Vinci Code should have a very big notice on the cover warning that it is not entirely composed of verifiable facts! The curious thing is that (as I understand) there are already many books commenting on it and many reviewers - let alone members of the public - seem to accept its allegedly historical background and interpretations as more or less scholarly truth, however poorly they may stand up to scrutiny. I am sure, Roger, that you are not the only one to be confused by it but at least you can recognise an embellishment! Andrew James Roger Bailey wrote: snip The Saint-Surplice meridian is a key element in the best selling novel The Da Vinci Code by Dan Brown. snip This confused me as I expected the Paris Meridian to go through the Observatory of Paris ... The meridians are quite different but the novel brings them together. This is not the only fact embellished by the author to set the plot for his novel. PRI Limited, PRI House, Moorside Road Winchester, Hampshire SO23 7RX United Kingdom Tel: +44 (0) 1962 840048 Fax: +44 (0) 1962 841046 www.pri.co.uk The Intelligent Metering Company This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl -
RE: Gnomon Holes
Mike I asked this question (elsewhere) a few months ago in connection with a mid C17 dial. The holes are not just punch dots which would aid in placing a compass or marking the gnomon corners, but drilled right through the plate (neatly filled in this case, though not always). I believe (purely as conjecture I must say) that they were part of the laying out and indeed the marking process and not only denoted the gnomon corners but took pins against which a rule was laid. Other punch marks can be seen where compasses were centred to draw the hour circles for example but these do not go through the plate. On a double horizontal dial there are a lot of compass centre dots to be found! If you were, say, a London maker, most of your stock dials would probably be for its conventional 51d 30' latitude and using a scale on the bench or a workboard with a pin sticking up at the centre, a ruler could be held against the pin and easily aligned against each gradation on the scale in turn and the hour or other line scribed along it. Anyone who has made a dial or anything similar involving accurately placed straight lines by hand engraving or cutting will know that adjusting one end of a ruler to a defined position is much easier than fiddling with two ends, and having it positively located against a pin greatly reduces the chance of slipping or a line being marked out of position. If the rule had a little notch in it then it would take account of the diameter of the pin but a scriber point running a pin's radius away from the rule would do the same. The engraving on a good dial is accurate enough to see whether the lines go through the middle of the pin hole rather than tangential to the edge. It would seem to me to make a lot of sense to have a single layout carefully drawn which would cover manufacture for your local customers and could easily be replicated in a semi-skilled way onto a variety of dial sizes. Unfortunately I think we know very little about how the dials were actually made. Perhaps if country dials by makers who may be supposed to have made a very few individual dials tend not to have the pin holes and ones by supposedly prolific makers tend to have them it might add credence to the theory but I suspect that a lot of exceptions will exist. In any case I could see clear benefits in drilling the holes and using pins as I surmise even for a one-off because of the certainty of the lines converging accurately to the same point for minimum effort in positioning a straight edge. I have used a corner of something clamped to the plate for the same purpose of locating a long ruler when drilling was not a preferred option. Regards Andrew James -Original Message- From: Mike Cowham [mailto:[EMAIL PROTECTED] Sent: 29 October 2004 10:54 To: SUNDIAL Subject: Gnomon Holes I have just been asked the question to which I thought I knew the answer, but now I am not so sure. On English horizontal dials there are frequently two small holes drilled in the dial plate at the point where the root of the gnomon contacts the plate. The question is, 'What were the holes used for?' I understood it to be an aid for alignment of the gnomon but now I believe that these holes could have been used to take a pin or point of a compass/dividers during marking out. Perhaps some of you who still make such dials will use a similar method? Regards, Mike Cowham Cambridge UK This message has been scanned for viruses by MailControl. This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl -
RE: Roman Numerals - as a test message
Message text written by Frank King my guess is that the ratio would not be much different for clock faces. Message text written by Patrick Powers I have no data on this but because of the bias mentioned before (regarding the apparent better balance of a clock face when using ) I would suspect that the prevalance of could be even greater. It would be nice to know.. For what it's worth I agree with the web site Richard cited that iiij was the commonly written form and therefore it was natural to put it on a clock dial. As to why it continued after Roman numerals dropped out of widespread use, perhaps visual balance played one part and extreme conservatism another! I would say that virtually every English clock made between 1600 and 1900 used and not IV (and most of those made after 1900, too - and there aren't many made before 1600!). There is an interesting (but tiny) group of exceptions: for a few years around 1680-90 a handful of top London clockmakers, primarily the Knibb brothers Joseph and John and their circle, sometimes used a system called Roman striking wherein the hours are struck on two bells, a high pitched one representing I and a low one for V. If we call them ting and tong then 3 would be ting ting ting, 5 tong, 6 tong ting, 10 tong tong (two fives), 9 would be, subtractively, ting tong tong, and 12 tong tong ting ting. What about 4? By striking ting tong instead of ting ting ting ting two blows are saved. Most of these clocks either go for a long duration between windings - a month or three months instead of the usual eight days - or have complicated striking work, meaning that (especially in view of the spring technology of the day) saving power is important. So they strike ting tong at 4 and the dial reflects this by having IV not . The association is so strong that on seeing a dial of this period with IV one would be very surprised not to find Roman striking - and these clocks are very rare (I would guess perhaps a hundred are known, if that) and also valuable. I think a few English C17 sundials have V for 9 instead of IX though I have never seen a clock like this (surely this will bring a citation of a counter example from some knowledgeable list member?). I just assumed the maker who used V was not too familiar with Roman numerals! Digressing slightly on Roman vs. Arabic, the vast majority of English clocks (and watches) used Roman numerals until late in the 19th century. There was a blip in the first quarter of the 19th century when Arabic numerals were in fashion for a few years for clocks but did not displace Roman numerals even at that time. Later in the 19th century the proportion of Arabic numbered dials started to grow and became significant on domestic clocks, though still very low on public ones (compare this with vertical dials which are often public to some extent). I feel that Arabic numerals were much more widely used for clock and watch dials on the Continent. In England my impression is that Arabic numerals do seem to be more common on sundials than on clocks. Perhaps another list member can add a Continental perspective? Regards Andrew James N 51 04 W 01 18 This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl -
Rome, Piazza di Montecitorio
I was recently shown photographs of this Piazza and the obelisk by friends who stayed nearby and asked about its present functioning as a sundial. (I understand it was originally set up nearby as a sundial gnomon in Roman times.) The markings on the pavement seemed to me to be date related with perhaps a local time of transit taking account of EoT. I was told there is a slit in the globe which surmounts the obelisk so presumably a ray of light falls on the pavement with what I guess is a meridian line. I am sure some members of the list must have detailed knowledge of this; can anyone give more information please? Regards Andrew James N 51 04 W 01 18 This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl -
RE: sundial for the blind
Tom Egan wrote (08 March 2004 07:28) Let's see ... what senses are left? Smell. Taste. Sound. I'd better quit while I'm ahead. But perhaps we shouldn't rule them out completely, even if not appropriate in this particular application? (I'm going to leave out taste, though, as licking the parts of a public sundial might raise some eyebrows.) The increased temperature on one of a number of areas could cause a scent to evaporate most strongly there and be most detectible e.g. at one of a number of openings. And a mechanical linkage operated by temperature could alter the frequency of vibration of one tuned element relative to others so that a change in pitch could be discerned? (I don't think the straightforward effect of differential temperature on elasticity and linear dimension would suffice unless some odd material with something akin to a phase change near the operating temperature for the day could be used, nor would the change of speed of sound in air on a tuned cavity resonator or pipe be enough.) Not easy to accomplish - but when you next come across the Smellodial or the Suntuner, remember, you saw the idea on this list first (Or did you??) ;-) Regards Andrew James This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl -
RE: UK 240 / 110v equipment.
Following Larry's and Alexei's posts, not everyone realises that actually the UK uses 230V nominal now (and 400V 3-phase), not 240 (415), having changed, like the Netherlands, Ireland, and several other European countries, a few years ago. The reduced efficiency probably absorbs the output of a good number of UK wind farms in additional wiring losses, and I did ask at the time whether the Institution of Electrical Engineers (IEE) was going to change its telephone number from Central London 240 1871 (memorable as UK system voltage + year of foundation) to 230 1871 ... Patrick's reminder that the Health and Safety or similar rules may put a damper on your plans, John, is also worth bearing in mind. Lead in a dining room?? Hot?? Unfortunately a lot of changes and restrictions these days are made in the name of safety with no sense of perspective or proportion. (Of course many safety laws are very beneficial, but I could cite lots of idiotic cases - not on-list, though!) Regards Andrew James This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl - www.mailcontrol.com -
RE: Mosaic Sundials
There is I believe a mosaic analemmatic dial at a school in South London but I don't have details, though I may be able to find some out. Regards Andrew James -Original Message- From: John Carmichael [mailto:[EMAIL PROTECTED] Sent: 11 February 2004 13:45 To: sundial@rrz.uni-koeln.de Subject: Mosaic Sundials We've included a section on glass and ceramic mosaic sundials on the SGS website and have only found 4 examples in the whole world. This makes five. If any of you know of any other mosaic dials, please let me know. This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl - www.mailcontrol.com -
RE: Oblate Spheroid correction for computing distances?
Jim, For a simple mental arithmetic answer, I always understood that the English nautical mile (6080 feet when I was at school, about right for the English Channel - but 6076 or so for an International Nautical Mile) was by design very close to 1 minute of latitude, or longitude at the Equator. So 60 n.m. of 6080 feet = 69.09 English statute miles (of 5280 feet) = 1 degree. For metric users, the original definition (or rather the second, after they'd tried the length of a 1-second pendulum at Paris) of the metre was as 1/1000th of the quadrant of longitude through Paris. So taking 90 degrees = 10 million metres gives 1 degree = 111.111 km = 69.04 miles. Thus figures of 69 miles and 111 km are quite close enough for my everyday purposes. Multiply by cos(latitude) to get the length for a degree of longitude at any latitude. So here at 51 N, a degree of longitude is about 43.5 miles. The question of what do you mean by latitude has a bearing on the length of the degree of latitude. It is complicated by both the flattening of the Earth and the effect of the Earth's rotation on the apparent direction of gravity. The apparent direction of gravity affects what one practically measures as horizontal and vertical with level and plumb-line, as opposed to an imaginary vertical passing through the centre of the Earth - if you can decide where you think that is! At this point I'll retire and leave others who are better qualified to explain that and the resulting change in the length of a degree of latitude! Regards Andrew James -Original Message- From: J.Tallman [mailto:[EMAIL PROTECTED] Sent: 03 February 2004 15:58 To: sundial@rrz.uni-koeln.de Subject: Re: Oblate Spheroid correction for computing distances? Hello All, As previously mentioned, the earth is not a perfect sphere, and is distorted by the effects of gravity. So, is it flattened at the poles, or is it elongated at the equator? Is it a combination of both effects? I can envision a stretching effect at the poles, and a bulging effect at the equator, both of which I would think would affect the linear distances between theoretical degrees of latitude. If that is the case then I would think that the only true distances would be found in the mid-latitudes. I would really like to know how to calculate distances using the coordinates, as well. For example, the linear distance of a degree of longitude at the equator is greater than the linear distance that I would find here at 39 N. Every once in a while a sundial customer asks me how far away he can move before his sundial becomes inaccurate. I have always figured about 2 degrees of longitude is an acceptable range, but have no idea how to convert that to linear distance at a given latitude, other than manipulating the mapping sites that can handle coordinates. Best, Jim Tallman Sr. Designer FX Studios 513.829.1888 This message has been scanned for viruses by MailControl, a service from BlackSpider Technologies. This correspondence is confidential and is solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately. This message has been scanned for viruses by MailControl - www.mailcontrol.com -
RE: Dial design
An quick and easy way to make a helical dial for demonstration and experimental purposes is to take a wide strip of dressmaking elastic, with a whole twist, held on a frame which can be made for example by bending a wire coathanger. The hours can be marked in ink at equal intervals while it's flat. This isn't my own idea but I can't remember whose it was - so I offer apologies and credit wherever it is due. Regards Andrew James 51 04' N 1 18' W -Original Message- From: Frans W. Maes [mailto:[EMAIL PROTECTED] Sent: 01 December 2003 11:34 To: sundial@rrz.uni-koeln.de Subject: Re: Dial design Hi Richard, It seems you have reinvented Piet Hein's helical dial. See the home page of Egeskov Castle, http://www.egeskov.dk/english/sightseeing/index.htm and click nr. 25 on the map or in the list below it. John Moir showed already that the dial does not function well outside the equinoxes in BSS Bulletin 95.1. I give an explanation of this ill-behavior in my website: www.fransmaes.nl/sundials, choose Index and goto Kvaerndrup. Regards, Frans Maes 53.1N 6.5E - Original Message - From: Richard Hollands [EMAIL PROTECTED] To: sundial@rrz.uni-koeln.de Sent: 30 November, 2003 6:34 PM Subject: RE: Dial design I've just realized, thinking about it again, that the simplest realization of a 'helical' dial is a single sheet of metal given a half-twist of 180 degrees. So long as the edges are straight and the twist is distributed uniformly then the desired line o'light effect will be achieved. -
RE: BBC radio program(me) on sundials on 13 Dec.
Actually BBC Radio 4 long wave is on 198 kHz, 1514 metres, not the other way round. It's broadcast from Droitwich near the middle of England (grid ref SO929663, at a power of 500 kW) and from two smaller stations in Scotland, Westerglen and Burghead (each 50 kW). It also goes out locally on various MW stations around 720-774 and 1485 kHz as well as FM in the 92-95 MHz band. As far as I know it's not on the 5975 kHz frequency (which is BBC World Service in Central America and possibly other things). Andrew James -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: 28 November 2003 17:42 To: sundial@rrz.uni-koeln.de Subject: Re: BBC radio program(me) on sundials on 13 Dec. In a message dated 2003/11/27 02:50:54 PM, [EMAIL PROTECTED] writes: BBC Radio 4 will carry a 30-minute show on sundials on Saturday, 13 December at 1530 GMT. It's of course easy to hear in the UK, but anyone with a Web connection who can stream audio can also listen at http://www.bbc.co.uk/radio4/ or through the ether on long wave at 198 meters. I have a shortwave receiver that picks up BBC on 5975 kHz rather well. Will the program be at that frequency also? (This ancient computer won't handle streaming audio.) What would the frequency of 198 m be? Is that a band, rather than a frequency? Haven't heard of that band, but I'm a rank novice at this sort of thing. Let's see... 299792458/198 = 1514 kHz (Not correcting for the refractive index of air.) Have I messed that up? Thanks! John Bercovitz - -
DE HORUS SINICIS
Someone I know is currently translating DE HORUS SINICIS by T.S. Bayer [1735], which includes an illustration of a Chinese portable sundial. It was in the collection of Ernst Johann Biron, who was the chief magistrate of Russia at the time (and the empress's lover!). The dial is 17th century. Does anyone have any more information or precise dating on this dial, which is now probably in the Hermitage, St Petersburg? I can send a JPEG of the illustration on request off-list. Regards Andrew James 51 04 N 01 18 W -
RE: Pub Dials
The Chequers at Weston-on-the-Green (1d 13'W, 51d 51'N) had until about 4 or 5 years ago a dial painted on a wooden board. When I first saw it c. 1995 it had lost its gnomon and looked rather sad. Then it was replaced by a very smart looking dial in the same place, apparently painted on Perspex or similar plastic/acrylic, very neatly done and with a black wrought iron gnomon. Unfortunately the delineation is doubtful and the gnomon is certainly at an angle of about 60 or 65 degrees from horizontal instead of 52 and it would intersect the dial plane some inches above the centre implied by the hour lines. I expect it shows the right time now and then. I believe that advice was offered but not taken up. Very sad. However I think there are some bright lights outside the pub so you can use it equally well at night g. The other pub there, about 3/4 mile N, is the Ben Jonson and the stone dial looks probably 18th century though there is a possibility that it has been moved to its present location over the pub door. From memory it declines. There is a pub in Pembrokeshire (Dyfed) called The Dial Inn - at Lamphey mear Pembroke. Unfortunately it doesn't have a dial outside any more, though there presumably once was one; but there is a curious large square copper dial, apparently not that old, hanging on the wall in the bar. I couldn't decide quite what it was meant to be - anyone passing there? Regards Andrew James -Original Message- From: Colin Davis [mailto:[EMAIL PROTECTED] Sent: 11 August 2003 10:02 To: Sundial List Subject: Re:Pub Dials Hi! in the village of Weston on the Green on the Northants/Oxford border there are two pubs with sundials, one is painted ;the other looks like it is part of the original building. Only been able to look as I pass by,must get there and have a good look!!! Colin Davis G3VMU 52° 14' N 0° 52' W Northampton -
RE: Rod Gnomon Hole Placement
Patrick Powers wrote (Friday, August 01, 2003 9:10 AM) A propos the matter of the fixing of gnomons to stained glass dials - here's a bit of a conundrum for you. Would you have chosen the fixing holes on the Bucklebury dial? It declines about 13 degrees West yet the holes seem in a very strange place for that orientation... Was the dial perhaps wrongly made in the first place or was there a most interesting gnomon support Perhaps we shall never know. and John Carmichael wrote in reply (01 August 2003 22:01) Looks to me like that dial has big problems too. The 12 o'clock numeral is where it should be for a direct south wall, but the 6 am and 6 pms don't line up with the center. Andrew James was there last week. Andrew, do you remember if this is a south wall? Actually the Bucklebury dial is in a North wall or window :-) . It has been moved from its original site - probably at a (demolished?) house belonging to the Stevens family who lived nearby - to its present position next to the Squire's pew in Bucklebury church. Interestingly the precise cadencing of the shield indicates a Stevens who died earlier in the 17th century so this 1649 dial seems to have been made as a memorial or other remembrance by or for a descendant. It should face somewhat W of S as Patrick says. I didn't notice anything wrong with the delineation on that basis but it has been rather carefully and cleverly offset from the vertical centre line to give a better visual balance to the hours at the E and W edges by moving the vertical gnomon root - XII line to the W (now E, to the right seen from inside). Of course the top right numerals which look like VI and VII are really (I presume) VII and VIII, the final I in each case being hidden by the present leading - hence the odd VI-VI appearance which misleads at first glance. It would seem that the gnomon had a substyle foot as if for a direct South gnomon (which would have to have been folded westwards) as well as a pair of bracing stays, one each side, so that there are three lower fixing holes which is unusual I think - most have only two for a V-shaped foot or stay to the gnomon and omit the third. It is so carefully made and well drawn that I think a mistake is not very likely but that is only my suggestion. However the 1652 dial no. 33 on the SGS web page has a very similar 3-hole fixing - the date is very close and perhaps there is a connection there? The numerals and the cross patty, and the quarter hour marks, dots, and hour lines all appear extremely similar in draughtsmanship and form so would it be unreasonable to suggest the two dials might be by the same hand? I'd like to see a close up of the fly of no. 33! Re Ledbury: The church guide to the windows refers to this very rare 17th century stained glass sundial, and says that for many years it was upside down before the reglazing of this window by the Friends in 1988. I believe that when I saw it (June 2000) it was the right way up though of course that could have been wishful thinking :-) . Regards Andrew James -
RE: Rod Gnomon Hole Placement
John Carmichael wrote (01 August 2003 16:12): Because of the importance of rod gnomon attachment on stained glass sundials and the interest in the subject, I thought I'd make a Delta Cad scale drawing for the website showing a sideview of the hardware used to attach it to a pane of glass, using the bolting method. I should think that fixing a gnomon by just one attachment at its root would be problematic. For one thing it will be awkward to align accurately, but more importantly it will exert great leverage at the fixing point, and if the end is pushed by whatever means it will be far more likely to break the glass. Better to do what most of the old ones did and have a forked stay supporting the bottom end or the middle of the gnomon similarly fixed by nuts and washers into two more holes. That both assures rigidity and placement and ensures that very little strain is on any one of the fixing points, if properly fitted. It may be worth pointing this out to avoid short lived designs! Incidentally the outside of Bucklebury seems clearly to show the washer positions. Have you also considered the difference between drawing the hour lines on the inside and outside of the glass? The diagram shows the centre as outside, but if the paint is inside surely the gnomon root should pass through the dial centre on the inside surface, allowing also for refraction? Regards Andrew James -
RE: Rod Gnomon Hole Placement
I believe the Merchant Adventurers' Hall sundial has a brass or bronze gnomon like a which is fixed to a ring of the same metal surrounding the roundel in the dial on the outside. The gnomon root or dial origin is some way above the roundel and the actual gnomon. I think I can provide a clearer outside picture of that dial (and will send it to John off-list). Almost none of the old dials have the gnomon in situ. Feel free to use my wording, John. Re refraction: if someone painted the glass not in reverse it would need to be inside, though I don't know what is customary. Given that dials can be quite small I think even 3 mm or 1/8 could have a noticeable effect. It would seem simpler, if the Japanese protective cover can be as much as 10 away, to put it outside the whole glass/gnomon assembly, assuming the gnomon can be arranged to project less than that. As long as the cover has parallel faces it would make no difference to the angle of the sun's light. It would reduce the amount of sunlight transmitted at low incident angles - but then perhaps any frame holding the cover will interfere anyway. To have the cover intersecting the gnomon would produce a complication - and why not use it to protect the gnomon as well as the glass? Regards Andrew James -
RE: Rod Gnomon Hole Placement
John Carmichael wrote (04 August 2003 17:27) What about attaching the gnomon to the building and have it hang outside of the protective cover? I guess that as far as laying out the dial goes that would be equivalent to displacing the gnomon away from the dial by (thickness of cover) * (refractive index of cover - 1). Would anyone like to confirm that or give the correct answer if not? Regards Andrew James -
RE: On Meridian dials
There's a nice one on the floor of a church in Sicily - much smaller than the great Cathedral ones, about 6 metres long from memory, with an analemma marked around it. I think the church is at Castiglione di Sicilia - it's certainly somewhere immediately N to NE of Mt Etna. It has the latitude and longitude relative to Palermo marked as well. Is this on your list, Gianni? Regards Andrew James -Original Message- From: Anselmo Pérez Serrada [mailto:[EMAIL PROTECTED] Sent: 19 March 2003 17:43 To: sundial@rrz.uni-koeln.de Subject: On Meridian dials Dear dialists, As you all know, a Meridian Dial is a sundial with only one hour line: that of noon, which coincides with the meridian or N-S line if we measure local time. In Europe you can find them in some temples, the most outstanding ones being these: Date Height Temple City = 1437 50 m Holy Sophie Istanbul 1468 90 m S. Maria del Fiore Firenze 1653 27 m S. Petronio Bologna 1743 26 m S. Sulpice Paris 1786 24 m Duomo Milano By 'Height' I mean the height of the (pinhole) nodus from the ground in meters. Now my question is: does anybody know about some other remarkable meridian lines, maybe in other continents, maybe modern ones, or showing mean time, etc...? Best regards, Anselmo - -
RE: Sundials on the moon
Peter Have a look at http://www.redzero.demon.co.uk/moonhoax/index.htm Although I did not see the program, I think the answers to all that you saw on television will be found there, and in many other places. For example, in brief: Fluttering banner - it was on a springy wire to hold it out without any wind and there's no atmosphere to stop it moving Distant hills - mountains a VERY long way away don't look it with no atmosphere but show the same pattern from a range of viewpoints Diverging shadows - uneven ground (try it with sugar and matchsticks on the kitchen table - this should be second nature to diallists on odd surfaces ;-) ) I expect NASA think (probably rightly) that a hoax theorist would exchange terrestrial rock for lunar rock at the first opportunity! A lot of people do seem to have looked at it though ... My local glossy free magazine ran a couple of was it a hoax? articles last year. I look forward to a future issue of it proving that Stonehenge was built by extraterrestrials, or possibly overnight by Merlin using magical powers, largely on the basis that we don't seem to have constructed many large stone circles hereabouts for the last 2000 years. Andrew James N 51 04' W 01 18' On 27 September 2002 09:38 Peter Tandy wrote snip that presupposes that the Apollo astronauts actually did go to the moon. A recent TV programme here in the UK showed what seemed, on the face of it, compelling evidence of strange irregularities in the photographs from the moon. ... Now, I'm not quite so sure.. snip -
RE: compass dial
It seems to me that the vertical offset of the base of a vertical rod arising from starting at the upper edge of the ordinary pole gnomon could prevent the shadow falling on the central compass rose unless the sun were fairly high in the sky. You may be able to judge the minimum solar altitude from your photos, Frank; for how much of a winter day would it be useful? On the other hand enough open vertical pole might be seen through the gnomon frets to cast a useful shadow. Is it possible that the central post holes were to take not a gnomon to show azimuth but a windvane? After all, windvanes were common enough on C16/17 portable dials especially the Nuremberg ivory diptychs. That also requires something fitting loosely and hence removably into (a pair of) bearing holes rather than a shadow casting vertical which could be fixed, and gives a plausible reason for double marking. Neither explains the Elias Allen dial, though, with a 180 degree rotated compass rose in the absence of such holes. Perhaps it WAS a mistake - engravers weren't immune from making them (I vaguely remember reading of a clock by a famous maker - even Tompion perhaps - with the signature upside down) and a major one like that is just the sort of thing that goes unnoticed until afterwards! Andrew James N 51 04' W 01 18' -Original Message- From: Frank Evans [mailto:[EMAIL PROTECTED] Sent: 05 August 2002 14:45 snip In one of the four photos I took I have now been able to see two small holes drilled in the gnomon. These are clearly for the reception of a removable vertical rod arising over the centre point. Thus the shadow of this rod would give the sun's bearing plus 16 points (180 degrees) Moreover, by listing the reciprocal the sun's actual bearing is recorded directly. snip -
RE: new dial link, a big work !
It should I think be www.dasypodius.com AJ -Original Message- From: Alexei Pace [mailto:[EMAIL PROTECTED] Sent: 08 August 2002 11:42 To: sundial@rrz.uni-koeln.de Subject: Re: new dial link, a big work ! The link doesn't work here... AP www.dasyposius.com - -
Heliochronometer by Homan
I have recently been shown an interesting brass heliochronometer made by W. Homan of Glasgow according to his patent 18,568 of 1911. (I hope to receive a copy of the patent shortly.) It is quite large, based on a 13 1/2 diameter hemisphere. It has two gnomons, upright brackets carried on and perpendicular to a circular plate 11 diameter. The plate has, over an adjustable 15 degree arc at its edge, a scale divided in minutes, and can be rotated by hand against an outer fixed ring marked with hours from 1 to 12 twice. Each upright carries a half analemma, one for positive and the other for negative solar declination (summer and winter), and a slit - with in one case a small hole adding a nodus to the slit - to project light onto the half analemma on the other upright 7 7/8 (200 mm) away. It is set for a latitude (not adjustable) of about 7 degrees North, and a time difference from the local meridian of 5 minutes (added to the reading, so it was sited just over 1 degree West). This indicates it was made for use not in Britain but somewhere tropical, perhaps West Africa or Ceylon. Has anyone come across other example(s), or information about this device or its maker? Andrew James N 51 04' W 01 18' -
RE: Heliochronometer by Homan
Brooke Thank you for that - and thanks Fred for sending me the file off-list. From that I now see that the US Patent 946,223 is actually for a design completely different from UK 18,568 of 1911 and the instrument I saw! As I understand that he made at least two other known mean time dials on yet another principle, Homan would seem to have been quite a prolific inventor in the field. Perhaps he took out other US Patents? But as you say apparently one can't search for the inventor on-line at that date. I'll have a look, in case, for other UK ones using good old paper-based technology! Andrew James N 51 04' W 01 18' -Original Message- From: Brooke Clarke [mailto:[EMAIL PROTECTED] Sent: 31 July 2002 17:03 To: sundial@rrz.uni-koeln.de Subject: Re: Heliochronometer by Homan All US patents are on line. Sources for free on line TIF viewers can be found under help\How to Access Patent Full-page Images. Older patents can only be accessed by traditional US class number or patent number, none of the other search methods will work. -
RE: Monumental Statistics?
On the North wall of the Close of Salisbury Cathedral, Wiltshire, England, is a groove with the word MERIDIES, which is apparently a noon mark acting in conjunction with the spire. The spire is just over 400 feet (122 m) high and the wall is nearly that far from its base. It was mentioned in BSS Bulletin 91.3 pp22-23 and also in Peter Ransom's A Dozen Dials. I hope to publish some more about it in the BSS Bulletin in the near(ish) future. Of course it's not as big as Mont St Michel (see http://maget.maget.free.fr/SiteMont/ for some details of that temporary dial) but it beats most other things - but wasn't there once a (now non-existent?) mountain dial with markers on the hillside somewhere? However the volume definition of size is a very good one for eliminating a noon mark! Andrew James N 51 04' W 01 18' -
RE: seminar
Tony Yes please for some pdfs when you are sending them out (I didn't seem to get your offer of some weeks ago?) - I am down to give a member's short talk to the Southern Section of Antiquarian Horological Soc in September and might find some of your images useful there, especially of the multiple dial model. I've used the cardboard ones from the Magdalen and Bear book quite successfully in the past. It has to be a short talk - one of three after the AGM - which I find more difficult than a long one, which I've done several times! I must think of a theme (preferably one on which I have some slides). Sundials in Sussex, perhaps - or in Jaipur! Regards Andrew -Original Message- From: Tony Moss [mailto:[EMAIL PROTECTED] Sent: 14 June 2002 10:42 To: Sundial Mail List Subject: Re: seminar Greg, I have to conduct a 15-30 minute workshop on horizontal sundials. Real basic stuff, how to use the sun to tell time, how to make and position a simple horizontal dial, etc.. Has anyone ever had to give such a talk and if so what type of preparation, materials, handouts, slides, etc... worked best. I recently gave a similar talk to a client Rotary Club (All about Sundials in 15 minutes) and prepared an OHP transparency which shows the essential relationship between an Equatorial Dial and a Horizontal Dial but also goes on to show vertical and Polar surfaces arranged around a common polestyle. It also includes a north-facing Vertical surface. The original diagram appears in Frank Cousins' book and I have always been impressed by its ingenious simplicity. My developed version in Adobe illustrator is in colour and you are welcome to a GIF or PDF copy if you think it would help. Just to 'gild the lily' a 3D model was also made which, in conjunction with a point-source halogen desk lamp, demonstrates the simultaneous functioning of all four dials 'before your very eyes'. There are JPEGs available of this from various angles together with a sunlit shot of the model outdoors. If 'one picture is worth 10 000 words' then perhaps one working model is worth many pictures. The only problem which results is that the concepts involved are immediately obvious to even a non-specialistwhich leaves you very little to actually TALK about ;-) Copies available to any list member on request. This is the same material which I offered/distributed some weeks ago. I retain the copyright of all my images but these can be freely used for any non-commercial purpose. Best Wishes Tony Moss - -
RE: Shadow Sharpener Again, and sunrise and sunset elsewhere
John Carmichael wrote: It seems as though the only practical use for a bead-in-hole is on the alidade of an equatorial heliochronometer Since for it to work properly, as John Davis pointed out, it must always be perpendicular to the suns rays. A noon mark (possibly with an analemma) would be another possible use I think. The +/- 23 1/2 degree change from equinox to solstice should not cause too much trouble. Perhaps one should make the hole very slightly elongated (along the polar axis) to allow for this? An unrelated question: does anyone know of a sundial designed to show sunrise or sunset in quite another, distant, place? Presumably it is just necessary to construct a plane passing through the nodus of the dial and parallel to the plane of the horizon at the other place, and mark the line where it intersects the surface of the dial? I should go away and work out the formula, which I suppose must equate to an Italian or Babylonian hour line on an inclining declining dial with the inclination and declination corresponding to the lat./long. difference? Thinking about this gives me an obvious explanation of why Italian and Babylonian hours as shown by a pin gnomon on a flat dial are marked by straight lines, (which always used to surprise me), as taking a plane through the gnomon tip and parallel to that of the horizon for somewhere on the same latitude but the relevant number of hours East or West in longitude, that plane intersects the dial plane with a straight line, and the shadow crossing that line is a notification of the Sun's rising or setting either that number of hours ago or in that number of hours time in the other place. Perhaps others may find this a helpful idea? Andrew James N 51 04' W 01 18' -Original Message- From: John Carmichael [mailto:[EMAIL PROTECTED] Sent: 07 June 2002 16:50 To: sundial@rrz.uni-koeln.de Subject: Re: Shadow Sharpener Again It seems as though the only practical use for a bead-in-hole is on the alidade of an equatorial heliochronometer Since for it to work properly, as John Davis pointed out, it must always be perpendicular to the suns rays. It seems Patrick's excellent instructions on how to calculate its dimensions and focal length would come in very handy if you were designing an equatorial heliochronometer. John John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: http://www.sundialsculptures.com - Original Message - From: Patrick Powers [EMAIL PROTECTED] To: sundial@rrz.uni-koeln.de Sent: Thursday, June 06, 2002 3:14 PM Subject: Re: Shadow Sharpener Again Message text written by INTERNET:sundial@rrz.uni-koeln.de John said: ...but do you think your formula could help determine the optimum size of the gap between the bead and hole of a bead-in-hole sharpener? Yes it can help but it's not the same! Strictly the process is different but the formula used as I suggested (where you place the pin hole at distance f for a hole of diameter D) instead gives the MAXIMUM distance of the pinspeck device from the screen or image. You should actually choose a distance that is substantially less than that given by the formula if you want a pinspeck device to work. The formula I sent for the pinhole gives the details for a specific optical situation that lies between two other forms of so called imaging which happens to be the best for the purposes of a pin hole camera (or shadow sharpener). Art is right that image formation is not achieved in the same way as it is in a lens but if you choose to define focusing as 'a means by which points in an object can be proportionately and spatially translated into corresponding points of an image' then the pinhole and the lens do the same thing - and you can consequently still talk of things like focal length too. That's why I (like some people in the literature) do use the same terms for both. But you do have to realise that it's not the same... The pinspeck - that's the 'bead-in-hole' device - operates somewhat differently. Here the bright points in an object cast shadows of the pinspeck itself (that's the bead) onto the screen or floor and it is these points of shadow that you see. It therefore looks like a negative image. Here the key things are: 1. That the bead must itself be large enough to cast a shadow at the distance it is from the screen. 2. The distance of the screen from the bead has to be less than (s^2)/L if the effect is not to be marred by other optical effects like diffraction.. So the formula gives a distance that you must be well within. 3. The thing needs light to work so it doesn't work well in half light and being placed in a penumbra effectively switches it off. Also if you are that close then the image size is usually too small and indistinct even in good light. Because, with a pinspeck, every other point than the one causing a shadow also
RE: difference between equinoxes and midsummer
I think the difference may be explained by the axes of the ellipse of the Earth's orbit not coinciding with the equinoxes and solstices. In other words, as perihelion and aphelion are not at the solstices (as John wrote, January 4th not December 21st), the difference in speed of traversing the orbit can therefore account for the differences in the times from spring equinox to midsummer and from midsummer to autumn equinox. The equinoxes and solstices are governed mostly by the inclination of the Earth's axis in relation to the direction of movement round the orbit, and not much by the varying distance from the Sun. Andrew James -Original Message- From: Willy Leenders [mailto:[EMAIL PROTECTED] Sent: 26 March 2002 11:04 To: sundial@rrz.uni-koeln.de Subject: Re: difference between equinoxes and midsummer Thank you Piero and John. But after your answers my problem remains. 1. The equation of time can explain no more than about 31 minutes. The difference I descirbe is 21 hours and 10 minutes. 2. I describe a difference between two parts of the elliptical orbit of the earth which are symmetrical with regard to the sun. It is not the difference between winter and to summer but the the difference between the time from spring equinox to midsummer on one hand and the time from midsummer to autumn equinox on the other hand. I look out for a further explanation. Willy Leenders Flanders in Belgium 50.9 N 5.4 E mailto:[EMAIL PROTECTED] -
RE: Equatorial Ceiling Dial
John, Fer, and others, John asked : Let's say you have a spherical room, built like a planetarium, where the walls curve up into the ceiling and you locate your mirror in the center. ... Would the sunspot be perfectly round all the time? I think that the image of the sun coming from any part of the mirror (I'm assuming it is a horizontal mirror for simplicity) is always circular, so that if the mirror is very small compared with the room the sunspot will approximate to a circle. However the circular image of the sun is blurred or enlarged by the apparent size of the mirror (as seen from the sunspot, more or less) and this enlargement will only be equal in all directions when the sun and its reflection are both at the zenith. From the sunspot, the mirror appears as an ellipse and from the zenith it is the special circular case. At sunrise and sunset it appears almost as a line so the enlargement is almost purely horizontal, and at intermediate altitudes the vertical enlargement of the circle is less than the horizontal. (The elliptical appearance of the mirror varies slightly as you move up and down the image of the sun, hence I write almost.) Regards Andrew James
RE: Emergency Sundial
Steve Lelievre suggested using arc tan 1/4 to find 15 degrees in emergency. A slightly better approximation is to go via sin(15) = 0.2588 and arcsin(0.25) = 14.4775 deg cf. tan(15) = 0.2679 and arctan(0.25) = 14.0362 degrees So, take your string and find a quarter of its length as before by two halvings. Start from the centre point and mark a point on a first line at the string's length away. From that point draw an arc (or mark a few points to indicate it) using the quarter string as radius. Go back to the centre and take the tangent to that arc as the second line. The angle subtended is arcsin 0.25 or about 14 degrees 29 minutes, close enough for practical purposes I would think. If you want to get still closer, then do it both ways and add the difference between them to the larger of the two angles to get 14 degrees 55 minutes. (And if you dislike estimating the addition to make rather than constructing it, then take two of the sine angles one after the other i.e. added together and go back one of the tan angles to subtract it.) Or of course you could just use the same process, with half the string length instead of a quarter, to go via arcsin 1/2 and obtain 30 degrees, then take the string and mark two points equidistant from the origin on the two lines 30 degrees apart, and use doubling the string to find the point midway between those two - hence bisecting the angle into two angles of exactly 15 degrees with no error at all. But we're getting close to terrestrial origami I fear ... Regards Andrew James 51 04 W 01 18 N
RE: Query about solstices
Surely the whole business of finding the solstice is like a slower analogue of finding noon by observing solar altitude? Just around noon the altitude changes extremely slowly, and it is hardly possible to judge the time of maximum altitude exactly. Here, today, noon is at 12:04:49 but even if we take 20 minutes before and after then the Sun will only be 8 minutes of arc lower. 1/365 of a day is about 4 minutes, and that interval either side of noon will see the Sun lower than its noon altitude by roughly 8 * (4/20)^2 = 0.3 minutes. I am neglecting change in declination, which is insignificant so near the solstice. Hence the benefit of taking altitude sights at known times some significant time either side of noon and calculating the instant of noon from those. Even if the times are only known by a clock which may not be correct, the result is noon as shown by that clock, which can thus be corrected. Conversely, if the clock is trusted, the longitude can be found. In general, one would allow for the rate of declination change for the day and its effect on the two readings. Similarly, by analogy, we see the advantage of taking declination readings (by whatever means) on noted dates a few days either side of the solstice. Andrew James
RE: Sundial link
I was fascinated by the use of gum metal - are you familiar with it, Tony? and the interesting statement Prior to the advent of the mechanical clock for telling time with (and that wasn't until the early part of the 14th century), the clocks you might be aware of are those of Cologne and Salisbury Cathedrals in Europe. But perhaps it's a live transcript? Andrew James
RE: Sundial link
Never mind, Tony, perhaps we should ask that (nowadays) deceitful but active chap mentioned further down on the same page: So they decreed that hence forth from the early part of the 13th century, all churches built would have the knave running due north and south in Europe, and on the south facing wall would be erected a sundial. P.S. Did he steal all those dials later, or did they just go when the buildings were rotated ? Andrew James -Original Message- From: Tony Moss [mailto:[EMAIL PROTECTED] Sent: 13 December 2001 11:45 To: Sundial Mail List Subject: RE: Sundial link snip Andrew James asked: I was fascinated by the use of gum metal - are you familiar with it, Tony? I've been chewing it over in my mind but find it a sticky problem. snip Tony M.
RE: Sundial Trick Photography
For vertical dials I would still rather stick with an SLR with a long lens (and a tripod!) because of the effects of perspective correction on the gnomon. Incidentally, the effect of a rising front / perspective correction lens can be more or less equalled - at no cost except a smaller image - by resolutely pointing the camera horizontally in front of your eye rather than tilting it upwards. You need a wider angle lens from the same distance, or alternatively have to move further away; and then you need to enlarge the image more as it will include the wall up to the dial and lots of ground (half the picture). Moving further away helps with the gnomon distortion, too - looking at it not up its length. The perspective correction or shift lens (and the view/technical camera equivalent Super Angulons and the like) is very expensive because quite apart from the mechanics it has to produce good images a long way off the optical axis - which is what you are doing when you move it right up its travel to take the high sundial. While John's photo of his Flandrau dial well illustrates the correction of the lines, if you look at the nodus it appears to lie NNE of its shadow, whereas the sun was really somewhere in the SE at the time. That's meant with no disrespect to his adjustment of the view of the dial plane, it's just a fact of geometry. But it occurs to me that one big advantage of a digital camera in all this is that with an ordinary horizontal dial on a high pedestal (not so easy with a very big dial, I agree) you can hold the digital camera at arm's length vertically over the dial and press the shutter, immediately examine the results, and repeat until you're quite satisfied. You will get the proper edge-on view of the gnomon (though its top will appear bigger as it's nearer the camera), whereas correcting perspective of a photo taken from the side appears to fold the gnomon down away from you. When I try this overhead method with a film camera I often wait days or weeks to receive a skewed blurry print of half a dial or one of my own feet. Andrew James
RE: Sundial Trick Photography
John Carmichael wrote :snip But I discovered that by using digital editing, you can stretch or compress a photo so that it appears that camera was directly over the dial! I discovered this while using the perspective and distort features of Adobe Photo Delux. snip Yes, it works quite well to a certain extent; but not altogether. Imagine a vertical direct East or West dial, with the gnomon parallel to but standing away from the surface. The proper face on view will show only the edge view of the gnomon. However your view from somewhere in front and underneath will show you the bottom surface of the gnomon as well. This will not disappear by the stretching in Adobe - nor, if it is a solid gnomon, will the part of the dial surface hidden behind (above) it come into view on your computer screen! So beware of that; I try to stand a long way back from high vertical dials and use a long focus lens. I don't agree with the idea that one should stand at essentially the same distance away from the wall as the vertical dial is up the wall, which makes the height of the dial submit the greatest angle to the viewer looking up at 45 degrees. That gives a massive 0.7 : 1 linear distortion (which as you say can be restored digitally) - but the gnomon's odd shape cannot. Horizontal dials on a high plinth aren't so easy, though ... Andrew James
RE: large sundial
Chris Lusby Taylor wrote: snip An alternative approach doesn't require thin or closely spaced lines. This is to use a nonius (after its inventor Pedro Nunes) which uses diagonal lines at an oblique angle to the radial hour lines. The position where the shadow crosses the diagonal line indicates the exact minute. This is seen on old quadrants and some sundials snip and Mac Oglesby: snip Chris, is this the same technique as used by Christopher Wren on the All Souls College Dial? snip Yes, this is similar in principle to the All Souls' dial; but there in effect the lines are dispensed with and the intersections marked by dots. There are at least two other related schemes: some dials (for example, one at Erddig, Clwyd, and one at I think Beddington Hall in Shropshire, both C18) have two scales divided into 2 minute divisions and offset by one minute between them, so that one scale has the lines for even and the other for odd minutes. In the same area is a small horizontal dial with rings which have 0, 30, 60; 5, 25, 35, 55; 10, 20, 40, 50; 15, 45 minutes marked, so achieving 5 minute reading with wider line spacing. These can be regarded as a sort of discontinuous nonius with stepped rather than straight diagonals. In my experience these are less common than diagonal scales (nonius), but perhaps sometimes are not noticed, particularly on a corroded dial. Andrew James
RE: ??? Roman numerals
[Kevin Conod wrote] These are all rather elaborate explanations . . . couldn't it just be that was used instead of IV simply because it is so easy to confuse IV with VI? [snip] [Tim Yu wrote] this simple explanation makes *very* good sense to me. I can easily see a potential problem of confusing IV with VI (and vice versa) when reading them at differing angles. Interestingly quite a few rural 17th century stone dials in England have the marks confused as if the carver didn't quite understand them either (e.g. going IX X IX, or V IV IIV). Two examples are at Warmwell (which uses V, or in fact V for 9) and Hilton (both Dorset). In Winchester there is also a modern dial (1960s?) with the Roman numerals wrong. At Woodstock, Oxfordshire, the church dial (C18 or early C19?) has IIV IIIV for 7 and 8 and so does a late C20 dial on the Town Hall! So illiteracy is not confined to long ago. It is very rare though not unknown to find an engraved clock dial with such a mistake - perhaps masons or carvers only made a sundial occasionally whereas clock dial engravers had more practice. Roman numbers on English clock dials almost always radiate outwards but on longcase painted dials when Arabic numbers were used the lower numbers are sometimes inverted and sometimes not (tumbling hours); Arabic chapters were also placed vertically more often than were Roman chapters. In old documents it is clear that the subtractive form was not always used and one sees iiij and viiij for 4 and 9. So I tend to believe the reason lay partly in custom and mainly in visual balance (and IX balances III better than does V, though I agree that all falls down for I and XI - but then there was not much choice). I feel the story about the clockmaker and the French King (variously Henry IV, Louis XIV etc) is nice but unlikely. But it's interesting that IV seems to occur so much more often on sundials than on clocks. It is so rare to see a golden period English clock (when arguably dial design was at its apogee) with a IV rather than , that IV is firmly associated with Knibb and a few other makers building movements striking Roman numerals on two bells, the lower for the V. This may well have been invented to save power, needing only 30 instead of 78 blows every 12 hours; useful if you are making a clock to go for a long time between windings - three months for some of Knibb's. The Great Clock of Westminster, with its famous IV, needs rather more power to drive it and to sound Big Ben, but at least there is further for the weights to drop (and to be wound up every few days)! Andrew James N 51 04 W 01 18
RE: engraving (roman) numerals
Jim McCulloch wrote: Let me recommend a low-tech skill that is not as hard as you might believe to acquire an acceptable ability at, which is carving directly on brass with (non-power) hand engraving tools, which, I believe, can still be bought from a few art supply or jewelry making supply sources. Yes, gravers are still available from jeweller's and watchmaker's suppliers. However they do not come sharpened in the way you will need them to use them. As far as I know there is just one book on hand engraving on metal that is usually quoted, and it's still available - these details are from Amazon: Engraving on Precious Metals A. Brittain Hardcover (first published December 1953) N.A.G. Press; ISBN: 0719800226 It is a good book (actually by three specialist authors), but it's certainly a skill that takes some practice. Many years ago apprentice engravers didn't even touch metal for the first couple of years, they just had to learn the drawing aspects with a pencil! However it's worth having a go and I found I could do something acceptable on a small scale after not too long. It's also helpful if you can find someone skilled to show you the angles of the graver and how they work. Andrew James
RE: Question about analemmic sundials
Troy [EMAIL PROTECTED] asked I'm curious about analemmic sundials. Is it possible to move the gnomon of the dial (along an analemma course marked with the proper days) to achieve the same effect? If I understand Troy correctly, to be asking about simple dials with figure eight analemmas on the hour lines, I think the answer is no as what is wanted must affect all the hour lines equally, which could be achieved by a rotation of the dial about the gnomon axis, and I believe no displacement of the gnomon will achieve this. I'm open to correction, though! Andrew James N 51 04 W 01 18
RE: Gnomon for Vertical Decliner
Arthur Carlson [EMAIL PROTECTED] writes: ... What you really want is readability, which is a compromise between brightness and blurriness for any pinhole. ... ... Extending this logic, a vertically elongated pinhole in a vertical plane might have some advantages over either of the other arrangements. Hmmm. Surely the problem with this is that the slit (which it will logically become if elongated enough) will not cast a line of light onto a mark on the dial at the same time throughout the year as the Sun's declination varies, except on the vertical (noon) line? (Of course this is absolutely fine if you just want a noon mark!) Moreover the elongation of the slit will decrease the accuracy of reading the declination. The former objection is of course overcome by making the slit polar instead of vertical so that you have an ordinary polar gnomon but which casts light instead of darkness ... I suspect some compromise is needed in the end - Tony's .gif showed how even for a very shallow countersink there comes a time when its bevel intersects the light. In any case the vertical hole may work better at higher latitudes with lower solar altitude, as it will become nearer to the normal hole anyway. But it's not obvious to me that the vertical hole will generally produce a much less readable spot than the normal one. Can anyone comment on that? Regards Andrew James
RE: Length of the year
According to Britannica's article on Hipparchus, ... observed the positions of the stars and compared his results with those of Timocharis of Alexandria about 150 years earlier and with even earlier observations made in Babylonia He proposed precession to account for the size of the difference and he gave a value of 45 or 46 (seconds of arc) for the annual change, very close to the figure of 50.26 accepted today. ... Knowledge of precession enabled him to obtain a better value for the length of the year ... his value for the tropical year was too great by only 6 1/2 [minutes?]. So, indeed, he had access to a long series of observations, but it doesn't answer the question of exactly how discovering precession led him to this value. Can anyone explain? To note just two of his other achievements, he produced the first star catalogue and was the first to specify position on the Earth by longitude and latitude; surely, he was a very smart fellow indeed. Andrew James
RE: beaded analemma date sequence
1, 6, 11 etc has of course the advantage of no smaller first interval. Following John's and Patrick's comments, the date sequence used on small C18 and C19 English clock date dials, when all dates are not numbered, was usually 5 10 15 20 25 31 (of course the dial had to allow 31 as the last as the hand or dial rotated in 31 days and had 31 divisions not varying with the length of the month). When the dial was a rotating disc showing through an open sector indicating against a pointer it went 3 6 9 12 ... 27 31, because closer numbers are needed to see where you are. To have 1 marked as such is unusual. I think that it may have been felt that with the minutes being numbered 5, 10, 15 ... it would look odd to have the dates numbered 6, 11, 16 ... (as well as being something different to engrave or paint!) and then the 31 arose as a reminder that 1 was to be found next to it. Andrew James
RE: Measurements on the Equinox
Fernando The rope is longer than the distance between the pegs x and y. (I hope the characters / and \ work as forward and backward oblique on your screen and you will need to look at this in a fixed width font I expect.) Pick a point * which I shall draw nearer the end x and move so that the rope is taut from * to x and also from * to y *_ / -_ / -_ x y Here * is shown above the line x - y Move to the other side of the line keeping hold of * with it taut again Now you have x y \ _- \ _- *- and connect the two points where you held * taut *_ /I -_ / I -_ x I y \ I _- \I _- *- like a kite shape You see that the line I I I I between the * and * is at right angles to the line x--y Regards Andrew James
RE: Time Exhibition
Well done Mike for acting on a nondial. I went to the Time Exhibition a Greenwich a few months ago and had mixed feelings. Please ignore the rest of this message if you don't want my personal reaction! It has apparently been done with no expense spared but I felt missed out on some of the most basic essentials of an exhibition - at least I go to an exhibition to see objects, which I know is a bit unfashionable in the museum design world these days. There were indeed many absolutely first rate, world class, important objects to see and it was wonderful to have a chance to look at them gathered together in London. However a lot of them in the sundial and horological categories are finely engraved brass etcetera and are best seen under a good light - without risk to them. Arranging them therefore in cases with (very interesting) manuscripts and the like which need near darkness for preservation means you can't see the metal things properly. The descriptive labels in the cases seem to be placed neither in numerical order nor in physical order corresponding to the objects. So having seen the small grey number next to something you can't find the dimly lit relevant label. If you happen to be carrying the erudite catalogue, containing some fine essays, things aren't improved because it doesn't appear to have numbers corresponding to those on the objects so you can't look them up in that either, and some very fine and little-known things - where you can't go away and read about them in a standard book - just get an almost footnote mention and little proper description. When you have found the description it sometimes tells you about the interesting things on the back of the object - for example a cubical sundial - but then have the designers condescended to mar their nice grey showcases with anything as useful as a mirror behind it so you can see for yourself? It's still worth a visit - and you can make up your own mind whether I'm just having a prejudiced rant! There are lots of good exhibits on aspects other than time measurement as Mike listed. Perhaps I'll go again in the next six weeks ... Andrew James N 51 04 W 01 18
RE: Nought at noon
Steve, Bob, and everyone, I do not think I have ever seen 0 on a sundial, nor on a clock. I seem to remember a sundial which had an Arabic 12 with all other numerals Roman - or was it vice versa? - but cannot think where. I would say that in England the simple cross + or cross pattee (more like the Iron Cross) is by far the most common other noon mark and at a rough guess is on 10 or 20 percent of old vertical dials; I don't recall seeing it on a horizontal dial. I can only think of two other marks for noon: at Holy Sepulchre, Holborn Viaduct, London, c 1670, there is a St Andrew's Cross X; and at Dorstone near Hay-On-Wye, Hereford, there is an interesting double sided equatorial dial dated 1823 (from memory) with what looks like a fleur-de-lys for summer noon though it is in somewhat rusty cast iron and I'm not absolutely sure how to interpret it. Andrew James N 51 04 23 W 01 17 46
RE: Longitude miniseries
On 10 July 2000 15:15 John Carmichael wrote: From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] To: sundial@rrz.uni-koeln.de Subject: Longitude miniseries 1. In the scenes showing the meetings of the Longitude Board with Harrison, on the wall is a large round map of northern Europe with London at the center. Around the perimeter of the map are the cardinal points of a compass. A single moving metal hand is attached at the center. This is indeed an internal weathervane driven by a shaft and gears from the actual vane on the roof. Several British buildings have or had them, including the East India Company offices and even some private houses (very large ones!) 2. To determine local solar time on the ship, Harrison used a sextant to look at the sun. How can a sextant, by itself, indicate the time? By determining times of equal altitude either side of noon and indeed the time when the sun reaches its highest altitude, noon is obtained (as well as the latitude, knowing the date). A compass would a) need to be accurate and corrected for magnetic deviation and b) would only be useful as described if the sky were clear at noon, whereas observations of altitude a short time either side of noon can be reduced to find the actual time of noon even if no sight is possible at that moment. For taking sights either side of noon of course a watch (a deck watch) is necessary but it is only its reasonable accuracy in the short term that matters, not its timekeeping over many days. Such a watch was used anyway to carry the time information to and from the chronometer(s) which were never moved from their resting place below deck. 3. Where are the four Harrison clocks today? Are they still functional? The four timekeepers H1 to H4 are all on show at the Old Royal Observatory, Greenwich, London, where they are indeed functional. H1 to H3 are kept running. However H4 requires lubrication - unlike H1 to H3 - and this means dismantling, cleaning, lubrication and reassembly every few years. The risk of damage inherent in this process, even though - in the hands of the most skilled and careful watchmakers to whom alone it would be entrusted - it may be slight, and the slight wear which running might cause, are nowadays felt to be good reasons why H4 - arguably the most important watch in the world - is no longer kept running. It was running until a few years ago. There are videos and simulation of its fascinating action. Several copies have been made of H1 over the last 50 years, and Malcolm Leach has almost finished a copy of H2, while Don Unwin has very recently made a copy of H3 which I saw running a week ago along with the H2 copy at Upton Hall, the British Horological Institute headquarters. The copy of H4 which Harrison made, H5, almost identical except with much less decoration, is in the Collection of the Worshipful Company of Clockmakers at Guildhall, London. It is also in working order though I am not sure whether it is now kept going - I rather think not. Harrison's late regulator clock is also at Greenwich in the same room as H1 to H4. One of his early wooden clocks was in the Time Museum and is now in the Chicago Museum. Another of his clocks is in Guildhall together with another clock movement. Apologies that all this is a bit off sundials but the Longitude film and story IS very interesting! Andrew James
RE: Water filled sundial at Herstmonceux
There are a number of these around (the one I remember seeing is at the Manor House Museum, Bury St Edmunds) - it's a registered design but I can't remember the details though I think it was 1960s or perhaps later. Basically the cylinder and liquid acts as a cylindrical lens which focuses a bright spot (the intersection of a bright line with the equatorial plane) onto the scale. It only works in summer because it's an upper surface equatorial! It would work with solid plastic or glass but I expect that it is made like that because liquid filled is cheaper ... Andrew James -Original Message- From: Steve Lelievre [mailto:[EMAIL PROTECTED] Sent: 07 June 2000 16:29 To: Sundial mailing list Subject: Water filled sundial at Herstmonceux, England, ... ... photo is at http://www.ualberta.ca/~droles/astro/astrav/Sun2.html
RE: Analemma Stuff
Thibaud Taudin-Chabot wrote it is simple arithmetic: our watch shows mean time, so the mean of the correction should be 0, otherwise your watch is fast or slow after a year. I thought just the same when I first saw the question - but then I thought again. I believe that the above condition means that the average length of the day (or hour, minute, second ...) shown by solar time must be the same as by the mean sun or corresponding clock. But you could declare solar noon today - at the meridian or allowing for the difference in longitude - to be at 12:02 or 11:57 or at any other time without affecting the going either of the sun or the clock. Therefore one can offset the EoT curve by a fixed amount with impunity in this respect. In fact this is exactly what we do by adopting a time at a longitude different from our own - or still more drastically by introducing daylight saving. I believe that the EoT curve IS chosen so that the average IS zero, which is the same as saying that if both its two sinusoidal components were reduced in amplitude to zero, then it would lie along the straight line of zero correction. This is entirely logical as if the magnitude were zero then it would make no sense to have a non-zero EoT. Adding up the two sine waves, at frequencies of 1/year and 2/year with their different zero cross points and amplitudes, quite naturally results in the curve we know with its particular crossing points. These dates are therefore not arbitrary but derive from the relationships of the phases (as they relate to our calendar) and the amplitudes of the two contributing components of its cause, the orbital eccentricity and the inclination. Andrew James 01 18 W 51 04 N
RE: gloomy houses
Patrick Powers writes: It is SRNO 4117 and Carolyn Martin and (I think) Andrew James did some research. Dial is from St Mary's Alverstoke, Hants Yes, it was I who did some research on it. I visited the Hampshire Records Office and examined microfilm of the Alverstoke Churchwardens' Accounts for 1749. I found that the churchwardens were Humphry Newdick Abraham and Richard Curry. (I am uncertain of the reading of Newdick - it may be Nendick; and Curry might just possibly be Carry or Corry.) Their expenditures for the year were respectively £17 13s 1d and £10 6s 11 1/2d. These seem mostly to have been on sparrow heads, hedgehogs, polecats, and the like, but the penultimate entry for Mr Curry is To a Dial £4 15s 0d. Unfortunately there is no record of to whom he made the payment. These are the churchwardens whose names appear on the dial. Frank Evans writes But be assured that the dial is, or at least recently was, fruitlessly mounted outside the South African church. Remarkable! But there. Frank, if you could send me a jpeg without too much trouble I'd be interested to see it! Back to the gloomy houses; I was told when I visited NZ about 10 years ago that a certain power station - somewhere between Auckland and Hamilton I think - had its extremely ugly back side facing the road and the smart glass front away from it because the UK designers had got it the wrong way round in just the manner described. Whether it's true or not, I don't know! Andrew James 51 04 N 01 18 W
RE: Diverging Light Rays
Tony Moss suggested using a non-diverging sunray after passing between pairs of posts 0.4mm apart for a heliochronometer. Art Carlson wrote: snip But this line is not unique. You will get such a line if the instrument is aligned toward any part of the sun's disk. end My idea is this: is it possible to combine the two points made? Arrange, say, two sets each of four posts with three 0.4 mm gaps between, one set having slightly wider posts but with the same gap, so as to make three light rays the outer two of which diverge by the same small amount - say 0.2 degrees - in each direction from the inner. Then balancing the appearance of the outer rays should give a rather more accurate estimation of the angle of the centre of the solar disc.Any takers? Regards Andrew James
RE: Anodising Afterthoughts
(off topic slightly - Napoleon and Aluminium) Interesting; I long ago heard the first story, that his second-best dinner service was gold, and understood that at the time Al was more expensive weight for weight than gold. So at first I doubted whether it would actually have been affordable for France to provide so many mess kits - or more to the point whether there was in fact enough free aluminum metal around in the world? Clearly it depends exactly when. My memory is suspiciously hazy, but I believe Al was discovered c 1825, after Napoleon I (Bonaparte) died, and first made in any quantity in the 1840's (e.g. suitable to make a large dinner service!) and by a better process by about 185x, so I think it was Napoleon III (Louis Napoleon). He was a great moderniser and keen on technical improvement - which applied to the armed forces with balloons etc; so your story sounds quite likely after all - with the proviso that one might have misunderstood both stories as Napoleon I without knowledge of the dates. Any historians able to confirm which Napoleon, or the story or dates? Regards Andrew James Winchester, England -Original Message- From: Arthur Carlson [SMTP:[EMAIL PROTECTED] Sent: Monday, November 15, 1999 7:57 AM To: sundial@rrz.uni-koeln.de Subject: Re: Anodising Afterthoughts The Shaws [EMAIL PROTECTED] wrote : ...aluminium is cheap... ..reminds me of the story that Napoleon had an extensive monogramed dinner service made from aluminium - just because it was the most expensive metal of his day. I heard the story differently, that Napoleon issued each of his soldiers an aluminum mess kit to take advantage of the reduced weight, despite the horrendous cost. --Art Carlson
RE: best possible angle for insolation and visibility
Fernando, Fellow diallists, Fernando asked: Given a certain latitude, how can we find the best angles for a sundial? For best I mean those that offer: a) the longest insolation during the day b) the longest insolation at the various seasons c) the best azimuth (declination) and the best reclination so the dial can be place as high as possible and still get to be seen comfortably (based on the angle, not on the size). and with the sundial in the top of a 6-meter tall (19' 8) column so as it can be the best possible visibility from the ground. At the same time it should work all year round for a certain latitude (in this case, 15 d 45' 5S), from sunrise to sunset. in trying to find a single plane dial; At the Arctic [Antarctic] Circle the sun just does not set on the N [S] horizon at midsummer. Therefore a single dial must face generally N [S] of horizontal otherwise it will not intercept that light. However, at the Arctic [Antarctic] Circle the sun just rises on the S [N] horizon at midwinter. Therefore a single dial must face generally S [N] of horizontal otherwise it will not intercept that light. From this we can see that only a horizontal dial will work in the polar regions to (just) satisfy both requirements. This is clearly the case at either pole where the sun travels along the whole horizon at the equinox. And, in fact, a horizontal dial will work in all regions (because while the ground is illuminated, so will be the dial) - the only problem here being that it will be out of sight on the top of the pillar, unless you either a) make it transparent and look at it from underneath or b) place a mirror above it and look at the reflection (BTW, is this a new (if rather impractical) idea of mine - can anyone cite an example?) In the Northern [Southern] hemisphere above the tropics, a direct S [N] vertical dial will not show earliest and latest hours at midsummer (or indeed at any summer date between the equinoxes). If we take a horizontal dial and tilt it towards either S or N, then the E-W line through the gnomon will be higher than that part of the dial to the S or N of the gnomon foot and will therefore shade the dial at sunrise and sunset either in summer or winter. Therefore I do not think a single dial will suffice unless it is actually horizontal. Two vertical dials will solve the problem - at 51 deg N a SW and SE pair work nicely. However as you go further towards the pole the angle between them must decrease until in the polar regions they have to be back to back e.g. N and S or E and W and sunlight arrives at one just as it leaves the other with a glancing illumination, so three (or more) become preferable if you wish at least one surface to be well lit at all times. Typically in England pillars or other structures (e.g. above a church parapet or roof) with four vertical dials (N, S, E, W) are reasonably numerous, while occasionally one finds a larger number of equally spaced ones (e.g. 6, Covent Garden, London; and 8, Douglas, Isle of Man). Omitting the N dial is often no great loss as the E and W ones can be used for more of the time anyway and there are quite a few of such E, S, W triplets (as well as some approximately SW, SE pairs). The complex multiple dials of Scotland are another subject altogether! I think that a vertical S (N) dial just works on the northern (southern) tropic. However, between the Equator and the Tropic, (and hence for Fernando's actual problem ;-) ) I'll now leave it to others to discuss the possible range of angles of a single inclining vertical dial, or between the pair of vertical dials required. Regards Andrew James
RE: Refs on japanning and metal surface colouring
Re: the Holtzapffel 5 volumes. I believe that vols 4 and 5 were reprinted some few years ago by Dover. Vols 1 2 and 3 were reprinted about 8 years ago (I think) in hardback by Tee Publishing. I think they were also reprinted by somebody else at about the same date but am not sure. I believe the first three were semi remaindered? and may be available from Tee as a special offer for about £25 which is a real bargain if still true - see http://www.fotec.co.uk/mehs/tee/lathes.htm for details. (Rita may not thank me though!) I do agree that the whole set makes FASCINATING reading if you're interested in the metal working / wood working crafts in general, and a long vanished perspective on a lot of the processes and materials, with some extraordinary examples of skill and labour illustrated in the ornamental turning volumes. Regards Andrew James snip -Original Message- From: John Pickard [SMTP:[EMAIL PROTECTED] Sent: 02 February 1999 22:48 To: sundial@rrz.uni-koeln.de Cc: [EMAIL PROTECTED] Subject: Refs on japanning and metal surface colouring I looked up the Holtzapffel ref on japanning Holtzapffel C 1864 Turning and mechanical manipulation Volume 3 Abrasive and miscellaneous processes ... Holtzapffel and Co, London pp. 1404+: japanning on metal, wood, etc. Lots of details on what to use, and how to do it. BUT I imagine that a lot of the ingredients would now be difficult to obtain.
Sundial setting - time and declination errors.
At a slight tangent to the sundial setting correspondence, I have a related question which I am sure someone will be able to answer. If one has a (declining) vertical dial which is accurately constructed in itself and with a correct gnomon, but which is mounted on a wall not exactly at the designed declination, how can one establish the error in orientation of the dial from observing the error in time (which varies with time of day and solar declination, as well as depending on the declination of the dial)? More generally one might also consider an error in latitude, but declination only would be a start. The formula might lead to an easy (?) way of determining a wall's declination simply by reading a portable dial placed against it temporarily (with the vertical line correct) and knowing the local solar time. There would be good and bad times at which to do this according to how rapidly the error in time changed with the error in declination. Is this a practical method? Several portable dials might be useful or required. I realise that one could measure the angle between the wall and a vertical dial (or an edge of a horizontal dial) oriented to show the correct time, but this would need the measurement or marking of an angle, which simply reading the time would avoid. Andrew James
RE: Latin Inscription
Hora Fugit Rapide Letumq.invadit inermus Lots of interesting replies so far! Yet another idea - my local classicist friends, much more learned than I, have suggested a) that it might have been intended to be inermes i.e. a plural - so meaning perhaps something like The hour flies rapidly and Death enters [us] defenceless ( I do prefer the understood [us] to [me, the sundial] being defenceless or unprepared. ) and b) that it is probably not an actual quotation from one of the usual Classical sources, but an assembly of words especially written. This might be more likely therefore to have a grammatical or typographical error introduced by a fallible author. I expect that someone will now cite an impeccable source! Regards Andrew James
A sundial motto query
I am trying to decide what may have been the original of a sundial motto
of which about half is missing. It is in Italian and as far as I can
read it is
IO NON ebro {about 30-35 letters missing}ans LANgU{about 10 missing}cARE
LA CAMPANO IL FERRO MA RISPLENDE SOLE
where lower case is uncertain (generally the top part of the letters
remains). I have photographs which show enough of a few other letters
to prove or disprove a suggestion, perhaps, but not to add much certain
information to the phrase.
I get a general idea of I'm not a drunken feeble thing dependent on the
iron clock but on the majestic Sun but not the detail. It is written
in a circle around a stone base which has weathered badly since 1908, so
the starting point might of course be wrong (and possibly missing)
though there is the suspicion of a dot after SOLE. Inside it are two
easy enough mottoes in Latin and Greek
HORA DIEM DEPASCIT EUNDO, and
(P)ANTA ANAPHEREI CHRONOS (transliterating from Greek)
I guess the Italian may be a well-known phrase somewhere, but not to me!
Can anyone help, please?
Andrew James
BSS member 629.
I found out about the mailing list from sundials on the Internet
