RE: Heliograph
Tony Moss wrote: In my impecunious searches of WWII 'surplus' stores back in the 1950s I came across a Portable Heliograph Set' in a pouch. It was simply a mirror about four inches across with a sighting hole in the middle. A length of cord attached it to a short rod with a bead on top. In use the mirror was held in one hand near to the operator's eye. The cord was then stretched tight and the 'bead' used to 'sight' the target. If the mirror was then rotated until a sunray coincided with the bead above the other outstretched hand a flash of sunlight would be directed at the target. I learned a different method in Boy Scouts: While looking through the hole at the target, you will also see an image of your face in the back side of the mirror. There will be a spot of light on your face where the sun shines on it through the hole in the mirror. If you tilt the mirror until the image of the spot coincides with the hole in the mirror, the sun will be reflected toward the target. This method might be considered less intuitive than the stick-string-and-bead method, but I actually find it simpler. I am fairly certain it is also more accurate. It also takes less equipment, so it can be carried out without preparation with any two-sided reflecting surface. And while we're on the subject, I would be interested in learning how the heliograph in Peter Mayer's jpeg is aimed. It's not as easy as aiming a laser or a search light because information on the position of the sun as well as that of the target is needed. --Art
RE: Heliograph
Bob Haselby and Tony Moss dialoged: This sounds like a signal mirror ... It uses double internal reflection in the hole to give a virtual image of the sun Any chance of a diagram or somesuch to show how this works Bob? It could work like this: Set up two sheets of glass and a mirror so they are all perpendicular to one another. There will be a faint image of the sun reflected in each sheet of glass, but also a still fainter image due to a reflection from both sheets. The direction of this third image is also the direction the sunlight will be reflected from the mirror, so if you tilt the assembly until the faintest image is superimposed on your target, they will see the light. This does not yet sound like a practical piece of emergency equipment, but maybe it will give somebody enough of an idea to figure out how real signal mirrors work. --Art Carlson
Re: Heliograph
Peter Mayer wrote: I'm attaching a tiny JPEG illustration, taken from an ancient dictionary, which accompanies the definition of 'heliograph'. The instrument definitely has a mirror! But as you'll see, it also incorporates a telegraph key and a sighting vane. My recollection is that they were used by military forces in the 19th century in places like India. (I have a half-baked recollection that Kipling refers to one in a poem...¿Is that a source?!) Good illustration, thank you. The telegraph key certainly makes it easier to use. Now I only have to learn Morse code and find someone else to talk to across the valey... When my sundial indicates the sun is shining (mandatory reference to sundial). - fernando -- Fernando Cabral Padrao iX Sistemas Abertos mailto:[EMAIL PROTECTED] http://www.pix.com.br mailto:[EMAIL PROTECTED] Fone: +55 61 321-2433 Fax: +55 61 225-3082 15º 45' 04.9 S 47º 49' 58.6 W 19º 37' 57.0 S 45º 17' 13.6 W
Re: A couple of items on the web concerning the sun
Hello There is a description of the first project using the obelisk as a gnomon, in the book cadrans solaires de Paris by Andree Gotteland and Georges Camus. The idea was from the famous Camille Flamarion in 1913 and some lines have been installed in 1939, immediately stopped by the war. Only few lines are still visible. The new project is driven by the French Sundial Commission, I think, especially by Denis Savoie, its president. The lines and numbers are made of yellow rubber, sticked on the ground. Trying to read the time on that particular sundial could be very dangerous due to the terrible traffic on the Place de la Concorde... François Blateyron [EMAIL PROTECTED] web.fc-net.fr/frb/sundials/ (cadrans solaires, sundials, sonnenuhren...) -Message d'origine- De : Richard Langley [EMAIL PROTECTED] À : Jim_Cobb [EMAIL PROTECTED] Cc : sundial@rrz.uni-koeln.de sundial@rrz.uni-koeln.de Date : mercredi 23 juin 1999 04:42 Objet : Re: A couple of items on the web concerning the sun PARIS - France inaugurated the world's largest sundial Monday, using an ancient Egyptian obelisk as the pin and Paris's famed Place de la Concorde as the dial. I don't think this is a completely new sundial. I think they've just given the old one that used to be there a facelift. Perhaps one of our French members could give us a bit of background on the old and new dials. There's very little about the old dial in the Cadrans Solaires Francais Catalogues.
heliograph
Maybe somebody can remember more of Kipling's poem referred to earlier than I can. Or even the title. It was about India, I'm fairly sure. Part went something like: Are you there, are you there, are you there? Three sides of a ninety mile square, With a helio winking like fun in the sun, Are you there, are you there, are you there? Sounds like a long-range instrument to me and certainly mounted on a tripod for this kind of accuracy. Morse, inevitably, I should think. And why three sides? I suppose a series of heliographs cannot send a message in a circle but I could be corrected about that. Any further help? Regards, Frank -- Frank Evans
Re: A couple of items on the web concerning the sun
-Message d'origine- De : Richard Langley [EMAIL PROTECTED] À : Jim_Cobb [EMAIL PROTECTED] Cc : sundial@rrz.uni-koeln.de sundial@rrz.uni-koeln.de Date : mercredi 23 juin 1999 05:55 Objet : Re: A couple of items on the web concerning the sun On Tue, 22 Jun 1999, Jim_Cobb wrote: http://www.foxnews.com/js_index.sml?content=/etcetera/wires/0622/e_rt_0622 _2.sml World's Largest Sundial - But No Sun Reuters 8:36 a.m. ET (1237 GMT) June 22, 1999 PARIS - France inaugurated the world's largest sundial Monday, using an ancient Egyptian obelisk as the pin and Paris's famed Place de la Concorde as the dial. The trouble was that the relentless traffic made it hard to follow the time lines, the same traffic made Paris Mayor Jean Tiberi 45 minutes late for the unveiling ceremony - and the sun did not shine. I don't think this is a completely new sundial. I think they've just given the old one that used to be there a facelift. Perhaps one of our French members could give us a bit of background on the old and new dials. There's very little about the old dial in the Cadrans Solaires Francais Catalogues. ~~ I've only found this page in french: http://www.an2000.fr/actu/projets/obelisque.html Gilbert Fousse # La Poste - F-60128 Mortefontaine # ~ 49N06'44 - 2E36'09 ~ [EMAIL PROTECTED]
Re: heliograph
Frank, It may be a surveying party for the triangulation of India: a square of four corners, with three sides being sufficient for signaling between the four stations. At those distances I suspect that only the heliograph could be observed with a theodolite during the daytime. Gordon At 12:47 PM 6/23/99 , you wrote: Maybe somebody can remember more of Kipling's poem referred to earlier than I can. Or even the title. It was about India, I'm fairly sure. Part went something like: Are you there, are you there, are you there? Three sides of a ninety mile square, With a helio winking like fun in the sun, Are you there, are you there, are you there? Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Heliograph
Tony Moss [EMAIL PROTECTED] In my impecunious searches of WWII 'surplus' stores back in the 1950s I came across a Portable Heliograph Set' in a pouch. It was simply a mirror about f our inches across with a sighting hole in the middle. A length of cord attache d it to a short rod with a bead on top. In use the mirror was held in one hand near to the operator's eye. The cord w as then stretched tight and the 'bead' used to 'sight' the target. If the mirr or was then rotated until a sunray coincided with the bead above the other outs tretched hand a flash of sunlight would be directed at the target. It all seems rather 'iffy' but I suppose was intended as an emergency device. Has anyone any experience of it? [...] Tony Moss When I was growing up my brother had a sun signaling mirror. I think he got it through boy scouts, though when I joined scouting later I never came across one. I remember that the instructions were printed on the back of the mirror. My understanding of it was that it was for emergency use, allowing one to indicate his position to another who is some distance away. In my mind I pictured the scenario of one lost in the woods seeing a search party (or search plane) and wanting to flash a light in that direction to indicate his presence. As I recall, the mirror was rectangular, about 4 x 6 inches; in the center it was double thick (a round 1-1/2 inch annular attachment giving the extra thickness), with a 1/2 inch clear hole in the center. What amazed me was that the user looked through the hole and saw an orange-yellow spot that indicated where the flash was going. I always wondered how that worked (and to this day do not understand it). If anyone can explain that to me I'd be much obliged. Jim --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- But there's no need for turning back 'Cause all roads lead to where I stand. And I believe I walked them all No matter what I may have planned. -- Don McLean, Crossroads
Re: Heliograph
Bob Haselby [EMAIL PROTECTED] wrote: Tony, This sounds like a signal mirror which were also contained in life jackets etc as survival gear. The more modern are quite effective and are great for annoying people on the beach. It uses double internal reflection in the hole to give a virtual image of the sun and so it is easy to hit what you are aiming at even though you are to far away to see the actual reflection on the opject that you are trying to hit. Bob San Diego I believe double internal reflection must be the explanation I was looking for. I'll have to give it some thought. I also remembered another detail after I sent my last message; the annulus had a colored portion, and I believe it was the colored portion that lent the color to the indicator spot which I described (it's been thirty years since I last saw this item... it's hard to recall all the details). I wish I knew where to buy one of these gems so I could experiment... On occasion I've looked in recreational equipment stores to no avail. Jim --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- It's a good thing that we don't get all the government we pay for.
Re: A couple of items on the web concerning the sun
I found a CNN item on the French sundial. It has more historical information than the Fox News version. http://www.cnn.com/TRAVEL/NEWS/9906/22/france.sundial.ap/ Jim --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- Custom will reconcile people to any atrocity. -- George Bernard Shaw
Re: Heliograph
Bob Haselby [EMAIL PROTECTED] wrote: Jim, I found one of these signal mirrors in the surf years ago. [description elided] You will also see the light ball at that spot . Then move your head and the mirror together until the spot lines up with the distant object. As I recall you can almost knock a person off there feet at hundreds of yards away. Bob Yes! This sounds very familiar. Thanks for the details. Jim === Of any stopping place in life, it is good to ask whether it will be a good place from which to go on as well as a good place to remain. -- Mary Catherine Bateson
sundial.org logon problem
Hi Robert: Just tried logging onto http://www.sundial.org and the title page came up which said welcome to www. sundial .org in red letters with a link to Highway Productions at the bottom. My screen says document done and no advancement is possible. Where's the rest of the website and what am I doing wrong? Thanks, John Carmichael
Re: Heliograph
On Wed, 23 Jun 1999, Tony Moss wrote: In my impecunious searches of WWII 'surplus' stores back in the 1950s I came across a Portable Heliograph Set' in a pouch. It was simply a mirror about four inches across with a sighting hole in the middle. A length of cord attached it to a short rod with a bead on top. In use the mirror was held in one hand near to the operator's eye. The cord was then stretched tight and the 'bead' used to 'sight' the target. If the mirror was then rotated until a sunray coincided with the bead above the other outstretched hand a flash of sunlight would be directed at the target. It all seems rather 'iffy' but I suppose was intended as an emergency device. Has anyone any experience of it? Good grief, Tony, that brings back memories. I tried one of those mirrors once, and it worked quite well. Unfortunately, I didn't think to have a confederate stationed at the 'target' and so no message was sent nor received. They were for emergency use, but could be surprisingly effective. An intriguing thread, indeed! John
Heliograph
Fernando Cabral wrote: As far as I know, what you call heliograph we just call mirror. Nevertheless, there can be other names and usages if you check with the different armed forces and other people with survival training. As to me, the only name I know is really mirror, even for those especially-made mirrors with a small hole in the centre (to be used to collimate the light ray). Again, since you can clearly use such a device to send Morse code you can say you write with the sunlight, than calling it heliograph should not be unacceptable. I'm attaching a tiny JPEG illustration, taken from an ancient dictionary, which accompanies the definition of 'heliograph'. The instrument definitely has a mirror! But as you'll see, it also incorporates a telegraph key and a sighting vane. My recollection is that they were used by military forces in the 19th century in places like India. (I have a half-baked recollection that Kipling refers to one in a poem...¿Is that a source?!) cheers, Peter Attachment converted: MAC Hard Disk:heliograph.JPEG.jpg (JPEG/GCon) (000176FF) -- Peter Mayer | [EMAIL PROTECTED] Politics Department | University of Adelaide | 'phone:+61.8 8303 5606/5610 Adelaide, SA 5005 | FAX: (+61.8) 8303 3446 AUSTRALIA | --
Re: Heliograph
And, as a geodesist, it would be remiss of me not to point out that the heliograph was preceded by the heliotrope, a device to make survey stations more visible from long distances, invented by the father of modern geodesy, Carl Friedrich Gauss, in the early 1800s. -- Richard Langley Professor of Geodesy and Precision Navigation On Wed, 23 Jun 1999, Peter Mayer wrote: Fernando Cabral wrote: As far as I know, what you call heliograph we just call mirror. Nevertheless, there can be other names and usages if you check with the different armed forces and other people with survival training. As to me, the only name I know is really mirror, even for those especially-made mirrors with a small hole in the centre (to be used to collimate the light ray). Again, since you can clearly use such a device to send Morse code you can say you write with the sunlight, than calling it heliograph should not be unacceptable. I'm attaching a tiny JPEG illustration, taken from an ancient dictionary, which accompanies the definition of 'heliograph'. The instrument definitely has a mirror! But as you'll see, it also incorporates a telegraph key and a sighting vane. My recollection is that they were used by military forces in the 19th century in places like India. (I have a half-baked recollection that Kipling refers to one in a poem...?Is that a source?!) cheers, Peter === Richard B. LangleyE-mail: [EMAIL PROTECTED] Geodetic Research Laboratory Web: http://www.unb.ca/GGE/ Dept. of Geodesy and Geomatics EngineeringPhone:+1 506 453-5142 University of New Brunswick Fax: +1 506 453-4943 Fredericton, N.B., Canada E3B 5A3 Fredericton? Where's that? See: http://www.city.fredericton.nb.ca/ ===
Re: Heliograph
Peter Mayer contributed My recollection is that they were used by military forces in the 19th century in places like India. (I have a half-baked recollection that Kipling refers to one in a poem...¿Is that a source?!) In my impecunious searches of WWII 'surplus' stores back in the 1950s I came across a Portable Heliograph Set' in a pouch. It was simply a mirror about four inches across with a sighting hole in the middle. A length of cord attached it to a short rod with a bead on top. In use the mirror was held in one hand near to the operator's eye. The cord was then stretched tight and the 'bead' used to 'sight' the target. If the mirror was then rotated until a sunray coincided with the bead above the other outstretched hand a flash of sunlight would be directed at the target. It all seems rather 'iffy' but I suppose was intended as an emergency device. Has anyone any experience of it? and then there was the mechanically luscious Mk.14 bombsight made by 'The AC Sparkplug Company'.still have ittoo beautiful to cannibaliseNow there's a sundialling challenge! Tony Moss
Re: Heliograph
Bob Haselby contributed This sounds like a signal mirror which were also contained in life jackets etc as survival gear. The more modern are quite effective and are great for annoying people on the beach. It uses double internal reflection in the hole to give a virtual image of the sun Any chance of a diagram or somesuch to show how this works Bob? - I understand 'total internal reflection' but 'double internal reflection err! yes!! err!! I should have paid more attention in Physics instead of yearning for the workshop! Tony Moss
Re: Heliograph; heliotrope.
Tony Moss described: ..snip... a Portable Heliograph Set' in a pouch. It was simply a mirror about four inches across with a sighting hole in the middle. A length of cord attached it to a short rod with a bead on top. ... snip ... It all seems rather 'iffy' but I suppose was intended as an emergency device. I recall such devices from the WW-2 years, as included in survival kits'' placed in rafts and life boats. Often the mirror coating was on metal (e.g.,brass) rather than on too easily breakable glass. There is a another similar device to the heliograph, or sun writer. -- In this case called a heliotrope, (sun turner, just like the garden plant.) The heliotrope was used in surveying, including the Great Survey of India. In either of these devices, a second mirror could relay the beam or ray onto the signaling-, or beacon-, mirror, so that a full range of bearings might be covered. There is also the heliostat, familiar to amateur telescope makers, where a tilted mirror is attached to a polar-aligned axis and rotated at half solar hour angle rate (to allow for the doubled angle of reflection.) A second mirror then directs the light in a convenient direction for viewing the solar image, or to 'feed' a spectroscope or other apparatus. There are variations of multiple-mirror setups that can yield a stationary solar image that does not rotate within the image plane, or which use special mechanical linkages to enable a single mirror to produce the stationary image. I suppose that if the motion were to be supplied by the observer as feedback to maintain the image in relation to a fixed target, the rotation mechanism for the mirror could carry an indicator for time, and so one would have a form of interactive sundial. Bill Maddux
Old idea?
John B. wrote in part: There is a sundial which is a disk with a rod for a gnomon running perpendicularly through its center. I understand the problem is that it can only be read from the top in the summer and the bottom in the winter. Has anyone tried making the dial of acrylic/perspex/glass? In the NASS Compendium, Vol.4-N0.2 June 1997 pp. (28 - 31) Casimir Pietroski described The Etched Glass Sundial. He gave details of his method(s) for fabricating such dials from glass. Bill Maddux
