Re: Coming equinox
The U.S. Naval Observatory http://aa.usno.navy.mil/AA/data/docs/EarthSeasons.html is a source I trust. It gives the following (precision to the minute) d h d h m d h m 20002000 Perihelion Jan 3 05Equinoxes Mar 20 07 35Sept 22 17 27 AphelionJuly 4 00Solstices June 21 01 48Dec 21 13 37 so it appears that your values are better. Jim 40N45, 111W53 -- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | PTC | Salt Lake City, UT | (801)-588-4632 | | | 84108-1202 | Fax (801)-588-4650 | -- -- It's a morbid observation, but if everyone on earth just stopped breathing for an hour, the greenhouse effect would no longer be a problem.-- Newsweek Senior Writer Jerry Adler, December 31, 1990
Re: Coming equinox
I used xephem 3.2.3 to solve for when solar declination = 0.0 and got 2000 March 20 7:30:59 UTC. Xephem calculates that the declination of the moon at that time to be 2:50:47.5 (degrees:minutes:seconds). If you would give me your latitude and longitude I can compute the azimuth of the moon at its rise and set for your location on that date. Jim -- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | PTC | Salt Lake City, UT | (801)-588-4632 | | | 84108-1202 | Fax (801)-588-4650 | -- -- There must be more to life than sitting wondering if there is more to life.
Re: Metric v's Imperial.
Tony Moss [EMAIL PROTECTED] wrote: The US of course still use Queen Anne's gallon which the Imperial system replaced with a larger unit later on. We often forget this when comparing fuel prices. Tony Moss I guess one could say that Queen Anne's gallon has outlived the imperial gallon which was supposed to replace it... When people get in a huff about how backwards we Americans are for still using inches, pounds, c., I like to reply that the SI still uses the second which is also a ridiculous unit of measure. Quantum units are natural units, but perhaps it's not the most convenient to measure distances in compton radii. The radian is a natural measure of angle, but I would suppose everyone subscribing to this list uses degrees, minutes, and seconds. For example, I haven't seen any of the recent discussion about human visual acuity conducted in terms of radians. Jim 40N45, 111W53 =-= Do not do an immoral thing for moral reasons. -- Thomas Hardy
Re: metric
Dave Bell [EMAIL PROTECTED] wrote: Try Russia: Not only do they have 5 (and somtimes more) grades at the pump, up to 110 Octane (unheard of in the US since the 60's, except for boats and aircraft), but a typical upper-middle grade, maybe 90 Octane, sells for around 6 Rubles, about $0.23/14 pence, per litre! When you consider that the Russian State is in NO economic condition to subsidize consumer fuel prices, I have to think *we* are getting shafted! Dave I think you're right. As low as the US price is compared to European standards, quite a large portion of the price is Federal tax. Not long ago when the price of oil dipped, the majority of the price at the pump was tax. Jim40N45, 111W53 =-= In the world there is nothing more submissive and weak than water. Yet for attacking that which is hard and strong nothing can surpass it. -- Lao Tzu
Re: Any moon data site?
Does anybody there knows of any site where I can get information about moonrise and similar? - fernando Try http://aa.usno.navy.mil/AA/data/docs/RS_OneYear.html Jim 40N45, 111W53 --- -- | 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 what ... is it good for? - Engineer at the Advanced Computing Systems Division of IBM, 1968, commenting on the microchip.
Re: another eclipse question(s)
Hi moondialists: I have been watching the waxing moon each night as it heads towards the total lunar eclipse on January 21 4:41:30 Universal Time. Its apparent diameter seems to be increasing, which means that it is approaching perigee, right? If last month's huge full moon was nearly at perigee, then doesn't that mean that this month's full moon will also be near perigee? Wouldn't this cause the eclipse to last longer than an eclipse at apogee? Does anyone know exactly when the moon is at perigee this month? Thanks, John p.s. Please don't forget to check the moon's declination on your sundials during the eclipse, and let us know your results! According to the 2000 Astronomical Almanac, perigee occurs Jan 19 23 h UT. According to Kepler an orbital body moves fastest near perigee (equal area rule). The faster motion may outweigh the larger umbra--I don't know, though I suspect this to be the case. For more eclipse info, check out http://www.skypub.com/sights/eclipses/lunar/0001preview.html http://www.skypub.com/news/pr_eclipse000120.html http://sunearth.gsfc.nasa.gov/eclipse/SEextra/TLE2000Jan20.html Jim 40N45, 111W53 --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- The best thing about the future is that it comes only one day at a time. -- Abraham Lincoln
Re: another eclipse question(s)
Earlier I wrote: According to the 2000 Astronomical Almanac, perigee occurs Jan 19 23 h UT. According to Kepler an orbital body moves fastest near perigee (equal area rule). The faster motion may outweigh the larger umbra--I don't know, though I suspect this to be the case. On the web page http://sunearth.gsfc.nasa.gov/eclipse/SEextra/TLE2000Jan20.html I found this statement ... on July 16, 2000, Hawaii, Australia and Asia will see the longest total lunar eclipse in 140 years (since 1859). It will last 1 hour and 47 minutes. Looking in my Astronomical Almanac, I see that apogee occurs July 15 16 h UT. So I suspect that the longest eclipse times occur near apogee (as I implied above). Jim 40N45, 111W53 --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- I was walking in the forest the other day and a tree fell right next to me and I didn't even hear it.-- Steven Wright
Re: National Geographic special
Fernando Cabral wrote: So, as far as I can see, all this fuss and hype about the next new years day is but hype and fuss created and promoted by marketers that wanna sell more hotel rooms, more air ticks, more champaign... I am wrong? - fernando No, I believe you are correct. Clever marketers--they'll get to sell the turn-of-the millennium twice. And only the first one has potential to be troubled by the Y2K bug. Jim 40N45, 111W53 --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- Has it occurred to anybody else that many proprietors spreading prophesies of gloom and doom come Jan. 1 are gladly peddling food, water, battery-powered generators and other expensive wares on credit? -- John McCaslin
Re: Solstice Perigee
I decided to get out xephem 3.0 and do some calculations for the upcoming solstice/lunar perigee/full moon. Times are Mountain Standard Time (UT - 7). According to the xephem's solver, here are the time and other values at the solstice (I found this by using the solver to minimize the solar declination): Limb Equ: Geo 2000.0 12/22/1999 0:26:37 MST: RA Dec EaDst Elong Phase RiseTm SetTm Sun 17:59:59.17 -23:26:21.5 0.9837 7:48 17:04 Moon 5:34:25.99 19:57:13.2 356675 173.1 100 17:28 7:33 Lunar perigee (found by minimizing lunar-earth distance): Limb Equ: Geo 2000.0 12/22/1999 3:54:08 MST: RA Dec EaDst Elong Phase RiseTm SetTm Sun 18:00:37.55 -23:26:21.2 0.9837 7:48 17:04 Moon 5:43:46.84 20:11:20.4 356654 174.9 100 17:28 7:33 Full moon (full moon calculation built in): Limb Equ: Geo 2000.0 12/22/1999 10:33:19 MST: RA Dec EaDst Elong Phase RiseTm SetTm Sun 18:01:51.38 -23:26:19.0 0.9836 7:48 17:04 Moon 6:01:49.93 20:33:15.8 356731 -177.1 100 17:28 7:33 Finally, here is the upcoming perihelion, almost twelve days later (found by minimizing the solar-earth distance): Limb Equ: Geo 2000.0 1/02/2000 23:35:12 MST: RA Dec EaDst Elong Phase RiseTm SetTm Sun 18:52:59.00 -22:52:49.6 0.9833 7:51 17:12 Moon 16:13:27.56 -16:35:37.9 405794 -37.9 11 4:07 14:40 I am not claiming high precision; I used default settings for comparison tolerances, etc. Jim 40N45, 111W53 --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- Where there is a will, there is an Inheritance Tax.
Re: Twisted band sundial
Here is some info concerning the Piet Hein dial I got from this list some time back. Unfortunately, it appears that the URL has grown stale... Jim 40N45, 111W53 --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- I have never let my schooling interfere with my education. -- Mark Twain __ Date Fri, 28 Aug 1998 21:27:52 -0600 To Les Cowley [EMAIL PROTECTED], David Higgon [EMAIL PROTECTED], all sundial@rrz.uni-koeln.de From Roger Bailey [EMAIL PROTECTED] Subject Re: Spiral line solution extra See Helix Helios at http://www.egeskov-slot.dk/map/sun_dial.html for a wonderful helical dial by Piet Hein. It is at Egeskov Castle in Denmark. Thanks Daniel Roth for including it on sundial links Roger Bailey __ The Sundial Helix Helios is nine meters tall, and was given to Egeskov in 1989 by the multitalented Piet Hein. The time is shown on the twisting spiral.
Re: Act of 1752
May I recommend David Ewart Duncan's 'The Calendar' recently published by 4th Estate for an interesting insight into the calculation of the year etc. Paul Murphy I'll second that; it was a very good read. The full title is Calendar : Humanity's Epic Struggle to Determine a True and Accurate Year by David Ewing Duncan Here's an Amazon.com link if you want to learn more about it... http://www.amazon.com/exec/obidos/ASIN/0380793245/qid=942943896/sr=1-3/002-3183584-8100040 Jim 40N45, 111W53 --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- Repartee is something we think of twenty-four hours too late. -- Mark Twain
Re: Axial gnomons and riots
Frank Evans wrote: but I believe many had to pay rent and leases early. The law (in England) adopting the calendar change specified that this was *not* to happen, though I would not be surprised if unscrupulous landlords with uninformed tenants pulled off this trick anyway. Birthdays and various anniversaries were to be likewise adjusted so that a full 365 (or 366) days would elapse between the celebrations. That's why George Washington's birthday moved (as was cited in an earlier message on this thread). And the great festivals, e.g. Christmas, were displaced in time and this too caused a good deal of grumbling and discontent. Yes, I believe Christmas and Easter moved. The point was to move Easter back to it's 'correct' date, as determined by Gregory's blue ribbon panel. Frank Evans Jim 40N45, 111W53 --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- For my birthday I got a humidifier and a de-humidifier. I put them in the same room and let them fight it out. -- Steven Wright
Re: Act of 1752
Thibaud Taudin-Chabot [EMAIL PROTECTED] wrote: The year 1800 wouldn't be a leap year under the Gregorian calendar because 18 is not a mutliple of 4. Yes, this agrees with what I said about 1800 being treated as a normal year in England as a result of her adoption the Gregorian reform. Would England have adopted the Gregorian calendar right from the start in 1582 then 1600 would have been the first centennial leap year. Regardless of adoption of the Gregorian change 1600 would have been a leap year--under both the Julian and Gregorian rules 1600 is a leap year (as is 2000, which is what began this thread of discussion). The first century non-leap year for early adopters of the reform was 1700. However, 1700 was treated as a leap year in England and other late adopters. That is the reason England had one more day of adjustment when the reform was finally adopted. Did you know that by the same act of Parliament in 1751 the start of the year was changed from 25 March to 1 Januari, commencing in 1752 ? Yes. Jim 40N45, 111W53 --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- You can't have everything. Where would you put it? -- Steven Wright
Re: FAQ commentary
Art, You are, of course, correct. And if the FAQ committee prefers to go with your approach, I have no objection. The picture I had in mind was slowly turning the dial around to simulate various hours of the day. Since looking at shadows cast on the dial by the gnomon is the modus operandi for the dial, I thought it would be a good test procedure. Art Carlson wrote: Jim_Cobb [EMAIL PROTECTED] writes: I've thought of another tip for spotting worthless horizontal sundials (such as is sold in garden shops, etc)--if the shadow of the gnomon crosses the hour lines it's no good. This test requires only horizontal positioning, not polar alignment, and a lot will fail this test because the gnomon for cheap dials often does not intersect the dial plate at the convergence point for the hour lines. Actually it doesn't require horizontal positioning either, or even a shadow. For each hour line, you should be able to find a position for your eye such that the edge of the gnomon is superimposed on the hour line. If they ever cross, i.e., if you can ever see part of the hour line above the gnomon but not all of it, then the gnomon will not intersect that line in the dial plate, and the dial is worthless. --Art Carlson
Re: FAQ commentary
John Carmichael wrote: p.s. Surprisingly enough, we're a little short on basic math related questions. Any suggestions? Why aren't the hour lines evenly spaced on a sundial? Of course the intent here is for a horizontal (or vertical) dial, but the asker of this question would probably not know that term. I've thought of another tip for spotting worthless horizontal sundials (such as is sold in garden shops, etc)--if the shadow of the gnomon crosses the hour lines it's no good. This test requires only horizontal positioning, not polar alignment, and a lot will fail this test because the gnomon for cheap dials often does not intersect the dial plate at the convergence point for the hour lines. 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 | --- -- I can't think of any institution less qualified to determine the future of software in America than lawyers and bureaucrats in Washington. -- Americans for Tax Reform Director Ron Nehring
Re: Non-'D.S.T' Parts of the USA, and Australia ?
Luke Coletti [EMAIL PROTECTED] wrote: Greetings, An interesting URL on Standard Time. Does anyone remember when in '73 we (USA) didn't observe DST? http://www.standardtime.com/ -Luke Yes, I remember it well, but your facts are wrong in one particular--that year no standard time was observed. This was in the throes of the oil shock triggered by the Yom Kippur war (October 1973) and the resulting Arab oil embargo (it is still an item of controversy just how much oil shipments were impeded, but the word embargo triggered panic in the oil consuming countries). OPEC raised the price of oil from $3 to $11 / barrel (which, interestingly enough, is a figure that was recently revisited). In response Nixon and Congress moved to lower reliance in the U.S. on imported oil. One measure adopted by Congress was year-round daylight savings time. I remember going to school in the dark and the sun not rising until I'd been there for more than two hours. There were incidents of school children being hit by school buses because of decreased visibility. Mercifully this insanity lasted but one year. 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 | --- -- Frustration is a sign you need to increase your limit of incompetency. -- Michel Bourget
Re: Non-'D.S.T' Parts of the USA, and Australia ?
[EMAIL PROTECTED] wrote: Just to correct an earlier error, all of Michigan observes daylight savings time. My apologies for handing out dated information. In the early seventies when my brother attended Michigan State there was no daylight savings time in Michigan. I'm curious when (and why) they adopted it later... 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 | --- -- Television is a medium. So called because it is neither rare nor well-done. -- Ernie Kovacs
Re: Non-'D.S.T' Parts of the USA, and Australia ?
Can anyone give me a list of which USA States (or part-States), do NOT use Daylight-Saving Time - e.g. Arizona doesn't, but which others also don't ? Similarly, can anyone tell me what parts of Australia do NOT use Daylight- Saving Time - I think Queensland doesn't, but are there some more States ? Douglas Hunt. Michigan, Arizona, and Hawaii do not use DST in any part of the state. Parts of Indiana do not use DST. I am not sure this is a complete list. 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 | --- -- The fact that no one understands you doesn't mean you're an artist.
Re: size limits
I suggest that only members of the list who are affected vote on this. If you are like me and get your e-mail at work over a direct Internet connection, you shouldn't care about attachments. Of course I am affected by this decision. It matters a great deal to me that the data comes in a single packet when feasible instead of my having to search for it and save it in some coordinated fashion. 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 | --- -- The happiness of your life depends upon the quality of your thoughts: therefore, guard accordingly, and take care that you entertain no notions unsuitable to virtue and reasonable nature. -- Marcus Aurelius
Re: size limits
I'm not sure if Daniel Roth meant for each of us to vote on his limitation suggestion, but if so, I vote for 50 KB. Mac Oglesby Ditto. 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 | --- -- May you live your life as if the maxim of your actions were to become universal law. -- Kant
Re: GPS
My wife half-heard a piece on the radio this morning saying that GPS instruments would fail next week unless they had previously been modified to take account of some transmission changes. They would simply be unable to find a position. Sound a bit like the millennium bug. Does anyone have any information about this, please? Users were advised to contact their suppliers. I'm feeling lost already so can you help? Frank -- Frank Evans This sounds familiar. It's not a y2k problem per se, though it of a similar nature. I believe the issue is that a binary counter in the GPS systems had few enough bits that they would reach overflow during August 1999. I believe the limitation is on the satellites themselves. I don't have the book with me from which I learned this (it's The Millennium Bug: How to Survive the Coming Chaos, by Michael S. Hyatt), nor do I remember the precise date. I will look tonight. I believe that the book said that at the time it was written no solution had been devised. It sounds like this transmission modification must be the fix that DoD devised (or perhaps the transmission modification is simply the wrap-around of the counter). I wonder whether early GPS receivers will be able to cope... It reminds me of DOS's famous 640 K memory limit. 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 | --- -- Familiar things happen, and mankind does not bother about them. It requires a very unusual mind to undertake the analysis of the obvious. -- Alfred N. Whitehead
Re: Eclipses
You are correct that it is because the plane of the moon's orbit and the plane of the earth's orbit around the sun differ. I recall that the moon's orbital plane is inclined 5 or 6 degrees (not as extreme as the inclination of the earth's poles, which is 23.5 degrees). Here is a web site that describes itself Welcome to the Eclipse Home Page at the NASA/GSFC Sun-Earth Connection Education Forum. This web site is continually expanding and strives to be the ultimate resource for online information about eclipses. Please contact me with comments/corrections/suggestions or bad links! Fred Espenak e-mail: [EMAIL PROTECTED] http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html 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 | --- -- Nearly all men can stand adversity, but if you want to test a man's character, give him power. -- Abraham Lincoln
Re: Ya Gnomon?
Oops, I gave a bad URL in my last mail... Here's what Merriam Webster online has to say http://www.m-w.com/cgi-bin/dictionary I should have pasted http://www.m-w.com/home.htm My apologies, 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 | --- -- There's a mighty big difference between good, sound reasons and reasons that sound good.-- Burton Hillis
July lunar eclipse
There has been some discussion on this list of measuring time using a sundial near a lunar eclipse (at the time the moon is 180 degrees away from the sun and near the orbital node). Some may want to make observations and report to this list. I, unfortunately, do not have a high quality sundial. I do have a couple of astrolabes that I may use to get some measurements. According Sky and Telescope the maximum will occur July 28 11:34 UT. http://www.skypub.com/sights/skyevents/9907skyevents.html http://www.skypub.com/sights/images/9907ccluneclps_big.jpg 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 | --- -- Everything should be made as simple as possible, but no simpler.
Naive energy study
I cooked up a naive energy study for my home, Salt Lake City, to help me explain to my children why it is hot in the summer and cold in the winter. I used the xephem program as a calculator to compute the sine of the sun's altitude at fifteen minute intervals over the course of the day for March 21, 1999, June 21, 1999, and December 21, 1999 as viewed from Salt Lake City. xephem is freely available from http://www.ClearSkyInstitute.com/xephem/xephem.html It occurred to me that this may be of interest to this group, so I include the text below. Lines beginning with 'M' denote March, etc. Each line displays a time of day (Mountain Standard Time) and the sine of the sun's altitude. I also have gif and postscript files displaying the plot (each about 18 K) which I will send out on request. Perhaps someone will volunteer to make them available on a web page for others to access if there is sufficient interest. I also have alt-azimuthal plots for the three days (actually four days; I also did September 21 for this), in gif format, which I am also willing to send out or place on a web page. 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 | --- -- Technology...the knack of so arranging the world that we don't have to experience it. -- Max Frisch M,6.4913903,-0.00454486881357 M,6.7413897,0.0390374829229 M,6.9913891,0.0864242448893 M,7.2413903,0.134635254135 M,7.4913897,0.182715374524 M,7.7413891,0.230221231284 M,7.9913903,0.276867684141 M,8.2413897,0.322379606861 M,8.4913891,0.36656333899 M,8.7413903,0.409216261651 M,8.9913897,0.450147838368 M,9.2413891,0.489177790952 M,9.4913903,0.526135645054 M,9.7413897,0.560860929353 M,9.9913891,0.593203428712 M,10.24139,0.623023467673 M,10.49139,0.650192589515 M,10.741389,0.67459385983 M,10.99139,0.696122320429 M,11.24139,0.714685576033 M,11.491389,0.730203862409 M,11.74139,0.74261062 M,11.99139,0.751852761299 M,12.241389,0.757890678592 M,12.49139,0.760698601247 M,12.74139,0.760264674602 M,12.991389,0.756590983069 M,13.24139,0.749693464055 M,13.49139,0.739602086716 M,13.741389,0.726360340419 M,13.99139,0.71002548921 M,14.24139,0.69066800168 M,14.491389,0.668371339663 M,14.74139,0.643231779163 M,14.99139,0.615357765787 M,15.241389,0.584869772839 M,15.49139,0.551899603852 M,15.74139,0.516590026883 M,15.991389,0.47909439747 M,16.24139,0.439576151326 M,16.49139,0.398208559083 M,16.741389,0.355174715301 M,16.99139,0.310668383791 M,17.24139,0.264896030931 M,17.491389,0.218052152998 M,17.74139,0.170428945612 M,17.99139,0.122332027988 M,18.241389,0.0742777360504 M,18.49139,0.0275091931069 M,18.74139,-0.0141067996457 J,4.9322233,-0.0045415992146 J,5.187,0.0322647448622 J,5.431,0.0733608955786 J,5.6822233,0.116443679102 J,5.937,0.160617774946 J,6.181,0.205442220347 J,6.4322233,0.250620912805 J,6.687,0.29591789221 J,6.931,0.341090610759 J,7.1822233,0.385948078311 J,7.437,0.430288573731 J,7.681,0.473916094926 J,7.9322233,0.516639883976 J,8.187,0.558274124089 J,8.431,0.598638656708 J,8.6822233,0.637559203071 J,8.937,0.674867953984 J,9.181,0.710404408988 J,9.4322233,0.744015702765 J,9.687,0.775557460558 J,9.931,0.804894200052 J,10.182223,0.83189998 J,10.432223,0.856458864823 J,10.68,0.878465527095 J,10.932223,0.897825408632 J,11.182223,0.914455442418 J,11.43,0.928284244688 J,11.682223,0.939252356552 J,11.932223,0.947312633505 J,12.18,0.952430276304 J,12.432223,0.954583218552 J,12.682223,0.953762175069 J,12.93,0.949970700768 J,13.182223,0.943225122872 J,13.432223,0.933554564443 J,13.68,0.921000690069 J,13.932223,0.905617388634 J,14.182223,0.887470869374 J,14.43,0.866638940632 J,14.682223,0.843210992323 J,14.932223,0.817287665508 J,15.18,0.788980178295 J,15.432223,0.758410019775 J,15.682223,0.725708521245 J,15.93,0.691016093388 J,16.182223,0.654481904504 J,16.432223,0.616263129445 J,16.68,0.576524319385 J,16.932223,0.535436943294 J,17.182223,0.493178588237 J,17.43,0.449932655676 J,17.682223,0.405887686601 J,17.932223,0.361237259252 J,18.18,0.316180430032 J,18.432223,0.270922837342 J,18.682223,0.22565312609 J,18.93,0.180637677588 J,19.182223,0.136129833674 J,19.432223,0.09248657555
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
Re: New NASS Pages on the World Wide Web
Dear Friends, The North American Sundial Society is pleased to announce its new domain and Home Page on the World Wide Web. [...] The URL is: http://sundials.org Best regards, Bob Terwilliger I was struck by the lighted flat map of the world on the page, http://www.spiritweb.org/cgi/sunclock.cgi?width=300height=150usemapframe. it's a URL I can send to friends so they can see that (instead of having to get them to compile one of the programs I have that will accomplish the same). So I started creeping along the URL to see whether there was anything else of interest, and I found a calendar with moon phases http://www.spiritweb.org/cgi/mooncalendar.cgi Unfortunately, the phase display has little correspondence with the actual appearance of the moon at its various phases (they are more like eclipses if the earth's shadow were approximately the same size as the moon). These astrologers really crack me up. Their charts are off by a month because of precession, and the moon they display here has little relation to the actual moon. Jim === If astrology worked, all astrologers would be rich.
A couple of items on the web concerning the sun
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. [...] http://www.foxnews.com/js_index.sml?content=/etcetera/wires/0621/e_rt_0621_10.sml Summer Solstice Clash At Stonehenge Reuters 9:10 a.m. ET (1406 GMT) June 21, 1999 LONDON - New Age travelers invaded Stonehenge Monday, spoiling Summer Solstice celebrations before British riot police moved in to clear the ancient stone circle and arrested 22 people. Under cover of darkness, hundreds of travelers stormed through the fence surrounding the prehistoric monument and police in riot gear, backed by dogs and horses, responded by evicting some 1,000 people from the site. They literally trampled down the fence and ran into the stones, jumping over them, sitting on top, hurling all sorts of objects at police,'' said a spokeswoman for Wiltshire police in southwest England. They were throwing all kinds of things and we believe there has been some damage to the stones themselves,'' she said. There is a history of violent clashes between police and New Age travelers, whose alternative lifestyle often leads to mass congregations at summer festivals, ecological protests and anti-authority demonstrations. [...] 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 | --- -- Have more than thou showest, Speak less than thou knowest. -- Shakespeare
Re: New NASS Pages on the World Wide Web
Robert Terwilliger [EMAIL PROTECTED] wrote: Dear Friends, The North American Sundial Society is pleased to announce its new domain and Home Page on the World Wide Web. We are releasing the URL to members of The Sundial Mailing List so they can get a preview. Please visit the site and send any comments or corrections to the Webmaster from the site. [...] The URL is: http://sundials.org Best regards, Bob Terwilliger My congratulations on an excellent site. The immediate appearance is of a site with a very polished and finished look. It's clear I'll have to spend some time visiting the various links. I had never seen the shadow sculptures before; they are amazing... Jim === The hardest thing in the world to understand is the income tax. -- A. Einstein
Re: Happy Solstice
I thought this millennium's last summer solstice would be in December,
2000, south of the equator. Let's not forget our friends in oz,
Brazil, and other southern locales...
Jon, I'd like a copy too, if I may.
Jim
===
For a marketing boost, label your sundials as Y2K compliant. Hundreds
of years from now dial enthusiasts will wonder what that obscure
designation means; those who know will marvel that it was such a big
deal.
Dave Bell [EMAIL PROTECTED] wrote:
First, I'd like to ask Jon to send me a copy!
Second, I'd like to extend my condolences to all who were hoping the Y2K
problems would be minor in nature! Who would have thought they would have
extended to actually *cancelling* next year's Summer Solstice?!?
:{)
Dave
Dear Diallists,
If anyone would like a photograph of this mornings sunrise, I would be happ
y
to email to them..if only to make it worth my while getting up at 4am this
morning and being tired all day! It was taken at 4.50am BST at a place
exactly on the Greenwich Meridian, about 10 miles north of London.
It's not the best quality photos, but it makes a nice momento of this
milenniums last summer solstice. I'm also trying to put together an animate
d
gif of this mornings sunrise, so if anyone's interested, please let me know
.
Best regards to everyone
Jon Urwin
Re: My new site WEB
Ciao a tutti! I'm pleased to announce that my Web site is opened at the address: http://web.tiscalinet.it/partena/index.htm May be it's poor and ruogh, but it's just to begin with. At the present it contains images of a few of my painted sundials. Ciao Angelo Brazzi Thank you for posting your web address. I enjoyed seeing the artistry of your painted dials. I also thank you for the English translation... I tried stumbling through the Italian using cognates and my high school Latin, but I understood the English much better... 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 | --- -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint-Exupery
Re: Easter ( a bit off topic)
I believe that for calculation by simple souls Easter is just the first
Sunday after the first full moon after the equinox of 21 March. But I
would like to find Easter several years ahead and do not know where to
find lunar phases except for the current year. Or is there a handy
table somewhere. There is one in the Oxford Companion to English
Literature, extending over hundreds of years but it ends at the year
2000. Can anyone help, please?
--
Frank Evans
Here is a C implementation of Meeus's Easter algorithm
#include stdio.h
#include stdlib.h
/* Credit to Jean Meeus. */
main(int argc, char *argv[])
{
int year, a, b, c, d, e, f, g, h, i, k, l, m, n, p;
if ( argc != 2 )
{
fprintf(stderr, Usage: %s year\n, argv[0]);
exit(1);
}
year = atoi(argv[1]);
a = year % 19;
b = year / 100;
c = year % 100;
d = b / 4;
e = b % 4;
f = (b + 8) / 25;
g = (b - f + 1) / 3;
h = (19 * a + b - d - g + 15) % 30;
i = c / 4;
k = c % 4;
l = (32 + 2 * e + 2 * i -h -k) % 7;
m = (a + 11 * h + 22 * l) / 451;
n = (h + l - 7 * m + 114) / 31;
p = (h + l - 7 * m + 114) % 31;
printf(Easter %d is %s %d.\n, year, n == 3 ? March : April, p + 1);
}
Re: Fw: frame grid method
Tom Semadeni ([EMAIL PROTECTED]) wrote: Hi Jim^2,[Sorry, couldn't resist.] Aren't we trying to lay out marks FROM a computer screen or a piece of paper TO the real thing on the ground? So aren't we trying to FIND the radii of the distance circles GIVEN the coordinates of the target point and the location of the second reference point that Ron refers to? That being the case here are my calcs using Ron Anthony's A and B when he first surfaced this two reference point approach on Tue, 25 May 1999 14:17:32 -0700 , after he awoke from his semi-sleep! ;-) You are correct. However, someone (John Carmichael perhaps?) posed the inverse problem, and that is what Jim and I answered. 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 | --- -- If a man's wit be wandering, let him study the mathematics. -- Francis Bacon
Re: frame grid method
I *really* like this scheme. Very clever... 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 | --- -- You know when you're sitting in a chair and you lean back so you're on just 2 legs and you almost fall over and at the last second you catch yourself? I feel like that all the time. -- Steven Wright Ron Anthony [EMAIL PROTECTED] wrote: All, I'm sorry I was only half awake when this thread started so forgive me if I'm off course. If I had to lay out a large dial (say 100 ft) to a high degree of accuracy (say .1 of an inch) I would plot all the points not as x,y co-ordinates. I would plot them all out as the intersection of two lines from two fixed points. To see what I mean pick 2 points that are well established, e.g., point A where the gnomom meets the dial face, and point B some number of feet due north (in line with the gnomon base) of point A. Every point on the dial face is now at the intersection of two tape measures that start at points A and B. Assuming that the dial face is flat the accuracy would be good as the tape measures used. For the points that are almost inline with the AB line, a third point C could be used as one of the points. Point C could be calculated from points A and B. Of course the computer would have to calculate all of the points for you. As a crude ASCII art: Point X is 30 1 1/4 from point A, and 22 3 7/8 from point B. (A metric tape measure would be a lot handier) B \ \ \ \ \ / X /C / / / / / / A
Re: Sundial for downed pilots
Art Carlson wrote: That's exactly what I had in mind. This is a rule that can be easily understood and remembered, as opposed to remember to ADD nine hours to the clock time for a three-quarter moon, if it is WANING. What I would like to figure out is the errors involved in both methods, given orbital parameters. [...] --Art Carlson Here are some rough parameters. The maximum deviation of the ecliptic from the equator is 23.5 degrees. In other words the maximum deviation of the point where the ecliptic meets the horizon from the true east or west compass point is 23.5 degrees. That's where my remarks about knowing the time of year and time of day comes in--it gives the information about this deviation. If you have a celestial planisphere, it probably has markings for the ecliptic and celestial latitude. Give it a good examination to get a feel for how the deviations behave over the course of a year and day. However, the moon does not lie precisely along the ecliptic, but can deviate from it by a maximum of about 5 degrees (I'm not certain of that max. deviation, and I don't have my books with me). Plus, there will be error in tracing out the ecliptic through the sky as I first suggested. In sum, the procedure I gave is pretty rough. 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 | --- -- Through infinite mist, software reverberates In code possess'd of invisible folly. -- Curt Sampson
Re: Urgent request.
http://bible.gospelcom.net/cgi-bin/bible?language=Englishversion=KJVpassage=Ecclesiastes+3:11matchno=7 Ecclesiastes 3:11 (English-KJV) He hath made every thing beautiful in his time: also he hath set the world in their heart, so that no man can find out the work that God maketh from the beginning to the end. 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 | --- -- I have an answering machine for my phone. Now when I'm not home and someone calls me up they hear a recording of a busy signal. -- Steven Wright Fellow Shadow Watchers, This is 100% on topic and somewhat urgent for me. The large bronze dial plate which I am about to engrave must bear the biblical inscription He hath made every thing beautiful in his time Can anyone give me 'chapter verse' for this please as I must be certain that I have it absolutely per the King James' version as erasers don't work on bronze :-) In particular does 'his' have a capital letter? Before now I've made a mistake in the workshop and found myself mentally reaching for 'undo'. If only it were possible! Many thanks in advance. Tony Moss
Re: Sundial for downed pilots
Arthur Carlson [EMAIL PROTECTED] wrote: I do think being able to look at the sun and estimate directions could be useful (in case you forgot to pack a compass, shame on you!). On my list of things I would like to do and know how to go about but haven't found the time is to investigate telling directions from the moon. I read an article in the magazine of the German Alpine Club a few years ago on this topic and found it incredible. With a Ph.D. in physics I think I can figure out how many hours to add or subtract in which direction to convert moon position to sun position and then to direction, but I bet very few people dumb enough to get lost at night without a compass can. But even without a watch, if you see the moon rising, you know that's east. And if the shadow is oriented straight up and down, then the moon is in the south. You don't need to know much more than that to find the nearest road. --Art Carlson Except for a new (which you can't see) or full moon, you can use the terminator as an indicator of a perpendicular direction to the plane of the ecliptic. Follow the implied ecliptic to either horizon to get a sense of east and west. If you're familiar with astronomy and can anticipate whether the ecliptic should be north or south of the celestial equator for the current date and time you can refine this indication of east or west direction. 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 | --- -- With lies you may go ahead in the world, but you can never go back. -- Russian Proverb
Re: Sundial for downed pilots
A minute ago I wrote: Except for a new (which you can't see) or full moon, you can use the terminator as an indicator of a perpendicular direction to the plane of the ecliptic. Follow the implied ecliptic to either horizon to get a sense of east and west. If you're familiar with astronomy and can anticipate whether the ecliptic should be north or south of the celestial equator for the current date and time you can refine this indication of east or west direction. I should have been a little more specific here: If you're familiar with astronomy and can anticipate whether the ecliptic should be north or south of the celestial equator at the two horizon points for the current date and time you can refine this indication of east or west direction. 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 | --- -- Few things are harder to put up with than the annoyance of a good example.-- Mark Twain
Re: Sundials not needing corrections
This kind of disclaimers are only found in the USA and on products from the USA ;-) - Thibaud Taudin-Chabot, home email: [EMAIL PROTECTED] (attachments max 500kB, in case of larger attachments contact me) That should be ;-( instead of ;-)... At least the relative sunburn danger sundial would be Y2K compliant, thus avoiding a soon-to-be booming area for unscrupulous lawyers. 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 | --- -- We strive to collaboratively coordinate resource-leveling materials. -- http://www.unitedmedia.com/comics/dilbert/career/bin/ms2.cgi
Re: update on Schmoyer sundial
Luke Coletti [EMAIL PROTECTED] wrote: For those interested the URL to Morrison Associates is listed below. I certainly hope that one of the most famous of gnomon designs will be recovered. Schmoyer's dial is a classic. http://www.shepherdswatch.ca/ -Luke Thanks for the link... These are beautiful, and reasonably priced. Do any of the subscribers to this list own any of these items? ... have any recommendations? I'm considering one of the explorer sundials. 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 | --- -- A printer consists of three main parts: the case, the jammed paper tray, and the blinking red light.
Re: Barn Yard Atmosphere
Hi Jim, Thanks for this wonderful unit of energy. I will use it in my next technical presentation. It beats out my previous favourite, firkins per fortnight (f/f). Firkins per fortnight, a unit of volume flow, is most often used as a measure of beer consumption by engineering students. 1 f/f = 2.9 liters per day. Been there, seen it, done it! Roger Bailey Walking Shadow Designs N 51 W 115 You must be using imperial firkins (at least that's the term we use in the U.S.). In an idle moment I decided to check this out using the UNIX 'units' program and was initially confused: % units you have: firkins / fortnight you want: liter / day * 2.433479e+00 / 4.109343e-01 Then I was inspired, recalling the difference between imperial gallons and gallons you have: imperial firkins / fortnight you want: liter / day * 2.922487e+00 / 3.421744e-01 and managed to get your conversion factor of 2.9. The firkins / fortnight unit reminded me of a unit of velocity someone once told me he especially liked: furlongs / fortnight. you have: furlong / fortnight you want: meter / second * 1.663095e-04 / 6.012885e+03 you have: furlong / fortnight you want: meter / day * 1.436914e+01 / 6.959357e-02 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 | --- -- African or European swallow?-- Monty Python
Re: a peculiar sharpener
[EMAIL PROTECTED] (John Carmichael) wrote: Actually, nobody has mentioned this yet but as a kid I remember that we used a pinhole to look at the image of a solar eclipse. Now I know that it is called a shadow sharpener... I remember many years ago during a partial eclipse looking at the shade under a young tree. On the ground was a profusion of pinhole images of the eclipsed sun, formed by the random gaps between the leaves. Subsequently I've read of this effect in astronomy magazines. It's worth looking for, if you get the chance. 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 | --- -- I threw spot remover on my dog and he disappeared. -- Steven Wright
Re: a peculiar sharpener
Earlier I wrote: I remember many years ago during a partial eclipse looking at the shade under a young tree. On the ground was a profusion of pinhole images of the eclipsed sun, formed by the random gaps between the leaves. It occurs to me that I should have mentioned that the tree's shadow lay in large part on a sidewalk. The pinhole images need to be cast on a pretty good surface to be easily visible. 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 | --- -- Every program has at least one bug and can be shortened by at least one instruction -- from which, by induction, one can deduce that every program can be reduced to one instruction which doesn't work.
Re: Shadow Sharpener
Gordon Uber [EMAIL PROTECTED] wrote: Roger, thank you for your post. The Shadow Sharpener being a pinhole camera, why not replace the gnomon with a pinhole? One then could center a circle on the image and determine the time from its position. To form a good solar image the plane of the pinhole needs to be transverse to the direction to the sun's rays. In fact, I believe near-perpendicularity may be desired. To accomplish this with a classic pinhole, the plane would need to rotate during the course of the day. Perhaps there is some clever scheme that would achieve this pinhole behavior without the need for mechanical intervention, but I don't know what it would be. That's the beauty of using a sphere to form an umbra--it needs no such rotation (although the distance between the sphere and the point where the shadow impinges upon the dial changes as the day progresses). 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 is better to suffer wrong than to do it, and happier to be sometimes cheated than not to trust.-- Samuel Johnson
Re: accurate vs. precise
why don't you Anglophones try the metric system? - fernando Perhaps you should consider us bilingual in terms of units. Technically inclined (and many other) Anglophones use both English and SI units with comfort, though we prefer one set for some applications and the other for others. I wouldn't suggest that someone who is bilingual should avoid using one of his languages... (just to relate this to a previous thread :-) 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 | --- -- My personal mission statement is I live up to the wild and vague promises made by salesmen.
Re: accurate vs. precise
Fernando wrote: Now, I hate when I see something like 2 yards, 2 feet, 5 inches and (the stroke of mercy) 1/8 -- It takes me several seconds to figure out how tall that person is! Now that's a tall specimen (2.57 meters)! By the way: does stroke of mercy make sense in English? - fernando No, I'm not sure of your meaning for that phrase in the context (though I have some guesses). English (at least in the U.S., I'm not sure about other locales) does have the phrase stroke of luck, but that's the only 'stroke' idiom that comes to mind. It also occurs to me to mention that being an anglophone is not at issue here. In the U.K. most units are metric. I think other commonwealth countries make primary use of the metric system. It is we in the U.S. who hold onto this 'English' system, which is ironic when one considers that the early U.S. pioneered using the decimal system in its monetary system, which I believed inspired the French after their revolution to make other measurements decimally based. 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 | --- -- Great works are performed not by strength, but perseverance. -- Samuel Johnson
Re: accurate vs. precise
Dave Bell [EMAIL PROTECTED] wrote (I believe tongue in cheek): Indeed! Why, just last night, I was working with furlongs and fifths of seconds... Dave It's interesting that you mention this. Over the last several weeks I have been reading Tolkien's Lord of the Rings to my children. It contains references to furlongs, fathoms, and leagues. My children are able to relate to these units because they are simple multiples of units familiar to them. This is similar to bilingualism inasmuch as it makes excellent (and not so old) literature accessible. As long as some want to dismiss the English system as having a silly basis, may I propose we consider the hour, minute, and second. These are ridiculous units for the same reasons. Originally the second was one-sixtieth of one-sixtieth of one-twelfth of one-half of a day. At present the official definition of the second is goodness-who-can-recall-how-many oscillations of the light emitted by a certain atomic electron transition (again, who can recall which?). Yet, how many SI units are derived from the second? How much pain would be involved in incorporating Swatch Time in a new international system of units and using that to replace SI? In fact, at the time the metric system was developed (in revolutionary France) a decimal time unit was also developed (this has been discussed in this forum before. One could regard Swatch Time as a marketing revival of this concept.) It didn't catch on, and France eventually went back to the second. But it would have been easier for us to use now than the second had it caught on. Then we can move on to consider degrees, arcminutes, and arcseconds. We could do geography in radians! After that, how about monetary units? Legal systems? Language? Cultural norms? Hair length? Etc. We keep using these units because they are familiar and not too inconvenient, and the transition would be inconvenient. In the U.S. we continue to use the 'English' system for similar reasons; we continue to use inches for much the same reason we don't have robust professional leagues for soccer (er, football)--one we like and the other we don't much care for. 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 | --- -- To question a wise man is the beginning of wisdom. -- German proverb
Re: Martian sundial
Hmmm, I wonder what the leading candidate for a prime meridian on Mars will be? (I know, I know, it's already been established). One could argue that this, the first 'observatory' on Mars, would be a good candidate. It was the locations of observatories (Paris, Washington, Greenwich, others?) on earth that competed for the honor on earth. Of course Swatch wants to muscle their way in with internet time. I say, let them build a state-of-the-art observatory first, then we'll consider (and reject :-) it. Of course they could argue that since the observatory at Greenwich has shut down they have a case... Jim_Cobb --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- If a man's wit be wandering, let him study the mathematics. -- Francis Bacon Here's another press release on the Martian sundial, from the University of Washington's point of view. Go to the cited URL at the end for the 2 illustrations. It's been a fun project to work on (and it's still got a long ways to go!) - Woody Sullivan * FOR IMMEDIATE RELEASE DATE: April 21, 1999 Sundial will mark passage of days, seasons on Mars - You could call it Martian Standard Time. The new time zone takes effect in January 2002 when a sundial designed and assembled at the University of Washington lands on the red planet aboard NASA's 2001 Mars Surveyor. The sundial project was announced today during a news conference at Cornell University in Ithaca, N.Y., which is creating the experiment that will contain the sundial. Once the sundial is in place, the public will be able to monitor the passage of Martian days and seasons via the Internet. [...] ** Prof. Woodruff T. Sullivan, III [EMAIL PROTECTED] Dept. of Astronomy, Box 351580 tel. 206-543-7773 Univ. of Washington fax 206-685-0403 Seattle, WA 98195 USA
Re: EOT=0
[EMAIL PROTECTED] wrote: Hello John and everybody on this list, I don't want to extend this discussion endlessly , but I am surprised to read that the value of EOT depends on longitude. [...] I believe John was referring to the (local civil) date (and time) of the occurrence of the zero EOT value; the date and time do depend on time zone, which is loosely coupled with longitude. I did not read his remarks as implying anything more than that. (His goal is to write a sundial manual for his customers, who may not be astronomically versed.) Of course John can correct me if I read his remarks or intent incorrectly... I agree with the rest of your remarks. 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 | --- -- Hateful to me as the gates of Hades is that man who hides one thing in his heart and speaks another. -- Homer
Re: WHEN DOES EOT=0
Hello all: Does anybody know the exact time (UT) when the Equation of Time equals zero this April 15th (or is it the 16th)? Thanks John Carmichael Tucson I used the solver in xephem version 3.0 to find the zero of the equation Sun.HA+12-UT (that's hour angle of the sun + 12 - universal time). and got the result 4/16/1999 3:04:36 UTC 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 | --- -- To stumble twice against the same stone is a proverbial disgrace. -- Cicero
Re: capuchin dial
The 007 Capuchin Dial is a PostScript program written initially by Eric MacPhereson, University of Manitoba and with a later revision by Andrew J Irwin, c/o Math 007, University of Toronto [...] Luke, Thank you for sending the info on the capuchin sundial. This looks fascinating. It is also timely--my daughter needs to take readings from a sundial for a girl scout badge she is working on and I thought it would be good to let her assemble this one and use it. I have altered the postscript file for local circumstances and read the directions carefully (several times). However, I don't fully comprehend step #9 9. Use the flap and slit from step #5 to point the dial at the sun. The light should make a long straight shadow along the 'horizontal' line across the top of the page. Can you elaborate, or point me to a site that will more completely explain what it is I'm supposed to do here? Thanks, 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 | --- -- We aim above the mark to hit the mark. -- Ralph Waldo Emerson
Re: capuchin dial
Whenever you don't understand something, just reveal that ignorance to many people and then perhaps you'll understand... At least, I think that just happened to me. I think the key is that I don't cut out the 'slit and surrounding flap' completely, but leave it attached on the side opposite the slit (Duh, that's why it's called a flap). If I'm right, then no further explanation is now needed... Thanks for your efforts, 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 | --- -- Television is a medium. So called because it is neither rare nor well-done. -- Ernie Kovacs
Re: Transit (off topic)
Does anyone know when the next Transit of Earth will occur (visible from Mars)? Perhaps one of the upcoming Martian landers could view the event! Troy Heck Turning again to Meeus' excellent book: 1905 May 8 1984 May 11 2084 Nov 10 2163 Nov 15 2189 May 10 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 | --- -- I prefer to be true to myself, even at the hazard of incurring the ridicule of others, rather than to be false, and incur my own abhorrence. -- Frederick Douglass
Re: A tad off topic....?
The following are the years from 1800 to 2100 in which February has no full moon. This is taken from Meeus's book. 180919152018 184719342037 186619612067 188519992094 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 | --- -- All history is but a romance, unless it is studied as an example. -- George Croly Jean Meeus's book Mathematical Astronomy Morsels http://www.amazon.com/exec/obidos/ASIN/0943396514/o/qid=921164695/sr=2-1/002- 5697572-2293064 lists months over a period of about two hundred years which are missing a lunar phase. I believe it lists 1961 as the previous year (before this one) without a February Full moon; it lists several others. I don't have this book handy right now. I'll send more info later... If you have the book, it's in the chapter titled something like months with five lunar phases. I believe it's the last chapter of the first section of the book. Jim
Re: double blue moon
Hello all: Will two full moons always occur in a March that follows a Febuary with no full moon? John Carmichael Tucson The second March full moon this year occurs at 22:49 UT. Therefore, if one moves east from London by a couple of time zones March has but a single full moon this year (relative to the local standard time) and it is April that has two. This suggests to me that it is possible in other years for this to happen when measured against UT. 1999 Phases of the Moon Universal Time New MoonFirst QuarterFull Moon Last Quarter D H M D H M D H M D H M Jan. 2 02 49 Jan. 9 14 22 Jan. 17 15 46 Jan. 24 19 15 Jan. 31 16 06 Feb. 8 11 58 Feb. 16 06 39 Feb. 23 02 43 Mar. 2 06 58 Mar. 10 08 40 Mar. 17 18 48 Mar. 24 10 18 Mar. 31 22 49 Apr. 9 02 51 Apr. 16 04 22 Apr. 22 19 01 Apr. 30 14 55 May8 17 28 May 15 12 05 May 22 05 34 May 30 06 40 June 7 04 20 June 13 19 03 June 20 18 13 June 28 21 37 July 6 11 57 July 13 02 24 July 20 09 00 July 28 11 25 Aug. 4 17 27 Aug. 11 11 08 Aug. 19 01 47 Aug. 26 23 48 Sept. 2 22 17 Sept. 9 22 02 Sept. 17 20 06 Sept. 25 10 51 Oct. 2 04 02 Oct. 9 11 34 Oct. 17 15 00 Oct. 24 21 02 Oct. 31 12 04 Nov. 8 03 53 Nov. 16 09 03 Nov. 23 07 04 Nov. 29 23 18 Dec. 7 22 32 Dec. 16 00 50 Dec. 22 17 31 Dec. 29 14 04 http://aa.usno.navy.mil/AA/data/docs/MoonPhase.html 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 is well to remember that the entire universe, with one trifling exception, is composed of others. -- John Andrew Holmes
Re: double blue moon
This reasoning relies on the mean length of a lunation. But the actual case is more complicated. See my reply to John on this same subject. 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 | --- -- Gregor Samsa awoke one morning to find himself transformed into an enormous software defect. -- Hindin Joseph I think it pretty well follows. Consider the latest possible case, where a full moon falls late on January 31. February will have no full moon, even in a leap year, with a 29.5 day sidereal month. That puts the next full moon on either March 1st or 2nd, and the *next* full moon will fall on March 30 or 31. I:31/01 23:50 plus 29 12:00 60/01 35:50 corr 61/01 11:50 corr -31 (leap year) 30/02 11:50 30/02 11:50 corr -28 -29 II: 02/03 11:50 01/03 11:50 29 12:00 29 12:00 III: 31/03 23:50 30/03 23:50 If the first full moon falls earlier on January 31, the third one will still be within March... Dave
Re: Fwd: Re: A tad off topic....?
Mark Wrigley [EMAIL PROTECTED] wrote: Not quite true. Last month Australia had a full moon at about 2am on Feb 1. In Europe it was still January. Quite so. Meeus (careful calculator that he is) explicitly notes his use of UT (and the dependence of such a calculation on the time zone). The fault is mine for not propagating that bit of information. 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 | --- -- Your weapons are no match for ours! People of Mars, surrender! Um, this isn't Mars. This is Earth. Earth? Earth-with-nuclear- weapons Earth? Yes. [long pause] Friend! -- James Nicoll
Re: A tad off topic....?
Jean Meeus's book Mathematical Astronomy Morsels http://www.amazon.com/exec/obidos/ASIN/0943396514/o/qid=921164695/sr=2-1/002-5697572-2293064 lists months over a period of about two hundred years which are missing a lunar phase. I believe it lists 1961 as the previous year (before this one) without a February Full moon; it lists several others. I don't have this book handy right now. I'll send more info later... If you have the book, it's in the chapter titled something like months with five lunar phases. I believe it's the last chapter of the first section of the book. 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 | --- -- Always go to other people's funerals, otherwise they won't come to yours. -- Yogi Berra This can't be true since February 1999 also didn't have a full moon. In addition since both the calander and the lunar cycle are periodic there must be repetition at some point. Previous Message: To all, Hmmm, hope I don't incur too much wrath over another moon question but I heard the other day that Feb 1865 is the only month in recorded history not to have a full moon (and hence be the only month in which a moon dial could not be used on its day of greatest accuracy - there; I got back on topic!!). It seems odd - is it to be believed do you think?
Re: A Pole at the Pole
Mike Shaw I am rather disappointed to learn that there isn't an Mike Shaw actual pole sticking out of the earth at the South pole to Mike Shaw mark the spot. I wonder if there is one at the North pole? Mike Shaw It would be really neat to drop an equatorial dial plate Mike Shaw over it and create an instant sundial, even if it would Mike Shaw only work for six month in each year - one at each pole Mike Shaw needed! Who'll volunteer to make the expedition? Mike Shaw (I knew we would get back on topic eventually) Mike Shaw Mike Mike Shaw [EMAIL PROTECTED] Mike Shaw 53.37N 3.02W The location of the pole (axis of rotation) changes. The following is extracted from an earlier email message I sent to this list: Jim Cobb The earth's axis of rotation differs from its axis of figure Jim Cobb (the maximum moment of inertia). The rotation axis moves Jim Cobb slowly around the axis of figure in a quasi-circular path. Jim Cobb The maximum amplitude of the polar motion is typically about Jim Cobb 0.3 arc seconds (about 9 meters on the surface of the Jim Cobb earth). This motion has principal periods of 365 and 428 Jim Cobb days. Finally, the motion is affected by unpredictable Jim Cobb geophysical forces and is determined from observations. Jim Cobb Jim Cobb I consulted The Astronomical Almanac, 1999, page B 60 for Jim Cobb most of the above information. The Explanatory Supplement Jim Cobb to the Astronomical Almanac contains further information Jim Cobb about polar motion, including a graph of about fifteen years Jim Cobb worth of such motion. 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 | --- -- Think like a man of action, act like a man of thought. -- Henri Bergson
Re: GMT and UTC
Earlier I wrote: The Explanatory Supplement to the Astronomical Almanac, mentions alternatives to atomic time under study that may offer improvements. (I don't have the book handy and cannot recall what they are. I will try to post a follow-up on Monday.) I believe that atomic timing technology is about fifty years old now... [...] Jim On pages 60-61 of the Explanatory Supplement to the Astronomical Almanac, is a discussion of modern timing technologies. 2.321 Quartz-Crystal Oscillators ... The performance characteristics may range from 10^-4 to 10^-13 in frequency stability per day. ... 2.322 Cesium Beam Standards ... laboratory cesium-beam frequency standards ... realize the second with the utmost accuracy (currently, 1.5 x 10^-14) and are, therefore, stable in the long term. ... 2.323 Hydrogen Masers ... The optimum stability reaches about 1 x 10^-15 for integration times of 1000 to 1 seconds. ... [S]ome hydrogen masers equipped with automatic tuning of the cavity and kept in temperature-controlled rooms have a long-term stability of the same order as the best cesium standards. ... 2.324 Rubidium Vapor Cells The rubidium clock is an appropriate device when a relatively low-cost clock is needed that has better stability than a quartz crystal clock. The rubidium clock can reach a stability of 1 x 10^-13 per day under the best conditions, but is subject to temperature- and pressure-induced frequency variations. Ringer et al. (1975) describe the design and performance of a clock for the GPS satellites. This clock has achieved stability of 2 x 10^-13 per day. 2.325 Mercury Ion Frequency Standard The mercury-ion frequency standard uses ions that are confined in a small region of space by an electromagnetic field trap. Thus the particles can be observed without having them collide with the walls, which would disturb the atomic resonance. The mercury-ion isotope Hg-199 has an extremely narrow microwave resonance line at 40507 MHz. Although this type of frequency standard should be a large improvement over the cesium standard, it has an unfortunately low signal-to-noise ratio, resulting in limited short-term stability. However, the long-term stability is very good, since integration can take place over a number of days (Winkler, 1987). I suppose I was incorrect to call these alternatives to atomic timing. Quartz is molecular; the maser is ultimately atomic in nature (or perhaps molecular, I'm not sure); and the others are all atomic. But they are alternatives to atomic cesium clocks. 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 | --- -- Have you noticed how the hole in the ozone layer has grown progressively larger since rap got popular? -- Dave Barry
Re: Sunset times (was: GMT and UTC)
[EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] wrote: snip ...as the time of sunset varies by as much as 6 hours from solstice to solstice (here in Michigan). end snip Hmmm... can someone help me out? A quick check of my astrolabe, with a plate for St. Paul, MN, gives sunset at about 1618hrs for the winter solstice, and about 1943 for summer - about a 3 1/2 hr variance. Am I missing something? Mike Blackwell For Detroit (assuimg EST is the time zone) xephem computes Limb 6/21/1999 4:55:05 EST: RiseTm SetTm HrsUp Sun 4:55 20:13 15:18 Limb 12/21/1999 4:55:05 EST: RiseTm SetTm HrsUp Sun 7:57 17:03 9:06 which agrees with your astrolabe computations. My guess is he was thinking of a six hour daylight delta. 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 | --- -- Your emotions are often a reverse indicator of what you ought to be doing. -- John F. Hindelong
Re: GMT and UTC
Dear Dialists... Regarding the assertion by David Higgon that the Earth makes a better clock than the frequency of an arbitrarily chosen atom. Unfortunately Earth's rotation is slowing down, so the atom is preferable, though admittedly less romantic. Presumably, if the human timekeepers endure long enough on the Earth there would be a noticeable difference in the day of the equinoxes and solstices. (the Earth's revolution IS NOT slowing down, which makes the atomic measurement necessary...please correct me if this is wrong) Troy Heck Ortonville, Michigan The Explanatory Supplement to the Astronomical Almanac, mentions alternatives to atomic time under study that may offer improvements. (I don't have the book handy and cannot recall what they are. I will try to post a follow-up on Monday.) I believe that atomic timing technology is about fifty years old now... Clock technology marches on: First shadow measurement of diurnal rotation, then clepsydras, then spring/escapement mechanisms, then pendulum clocks (which were accurate enough to lead to the notion of the mean sun and the equation of time), then atomic clocks, then ???. 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 | --- -- He that wrestles with us strengthens our nerves, and sharpens our skill. Our antagonist is our helper. -- Edmund Burke
Re: lunar eclipse
Well, that's interesting. I would have defined full moon as the time when the moon is most nearly opposite the sun, which would be the same as the time of maximum ecclipse. How else can it be defined? There must be something like a projection into the ecliptic. Art Carlson Perhaps the difference arises from measurement with respect to the celestial equator in one instance and the plane of the ecliptic in the other. Since the moon is not precisely opposite the sun, times measured for opposite can be different for the different coordinate systems. I'm not sure; I will see if I can find out tonight. 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 | --- -- In a museum in Havana, there are two skulls of Christopher Columbus, one when he was a boy and one when he was a man. -- Mark Twain
Re: lunar eclipse
Earalier I wrote: Now we know from my earlier messages that the Moon is one degree north of the ecliptic at the time of the full moon, and approaching crossing. Oops... It's south of the ecliptic at the time of the full moon. Sorry for the error. 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 | --- -- If I could drop dead right now, I'd be the happiest man alive. -- Samuel Goldwyn
Re: lunar eclipse
Here is the eclipse info from the 1999 Astronomical Almanac (p. A 79). I meant to include this in the last message, but sent it off too soon... Circumstances of the Eclipse d h m s UT of geocentric opposition in right ascension, January 31 16 38 02.180 Julian date = 2451210.1930807838 d h m Moon enters penumbraJanuary 31 14 04.5 Middle of eclipse 31 16 17.5UT Moon leaves penumbra31 18 30.3 [...] Penumbral magnitude of the eclipse: 1.028 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 | --- -- The difference between common sense and stupidity? Common sense has its limits.
Re: Latitude/Longitude
In fact the situation is further complicated by polar motion. The earth's axis of rotation differs from its axis of figure (the maximum moment of inertia). The rotation axis moves slowly around the axis of figure in a quasi-circular path. The maximum amplitude of the polar motion is typically about 0.3 arc seconds (about 9 meters on the surface of the earth). This motion has principal periods of 365 and 428 days. Finally, the motion is affected by unpredictable geophysical forces and is determined from observations. I consulted The Astronomical Almanac, 1999, page B 60 for most of the above information. The Explanatory Supplement to the Astronomical Almanac contains further information about polar motion, including a graph of about fifteen years worth of such motion. The closer one looks at astronomical reference frames, the more complexity is revealed. 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 | --- -- There is nothing worse than a sharp image of a fuzzy concept. -- Ansel Adams There's a difference between astronomical latitude and longitude and geodetic latitude and longitude. Prof. Charles Merry at the University of Cape Town should be able to help you out with the specifics of geodetic datums used in South Africa: [EMAIL PROTECTED] -- Richard Langley Professor of Geodesy and Precision Navigation On Wed, 13 Jan 1999, Anton Reynecke wrote: Apologies for this non-sundial question, but I do hope someone can help. I've always been under the impression that Latitude/Longitude is a universal and unambigious method of indicating a position on the earth but now I am not so sure In South-Africa, the National survey system is based on a Gauss conform system with the Clarke 1880 (Modified) Ellipsoid. It is fundamentaly the same as the wordwide UTM system, with a slightly different scale factor, and the width of a system is only two degrees in longitude, one on either side of a central meridian, whereas UTM covers six degrees. Now the National system is based on the the same projection but we are using the WGS 84 ellipsoid. That caused the Latitude of a fixed point to increase South by 2,04 arc seconds, and Longitude West by 1,06 arc seconds (approximately), and the projected co-ordinates changed by approx. 296 metres South and 27 metres West (Differences calculated by comparing coordinates from the old system with the new system, around Pretoria). I am under the impession that Lat/Long is astronomically fixed from distant objects, with the origin being the rotation axis of the earth, so how can the values be influenced by adopting a new ellipsoid ? What fundamentals am I missing? D. Anton Reynecke = == 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: Definition of Time?
If one is to delve into the question of What is time? it may be worth asking the companion question What is space? The theory of relativity tells there is a deep connection between the two. And the fact that the spatial question is asked less frequently may imply that it is an even subtler question. Bob Haselby wrote Without Time, everything would happen at once! Of course the word once depends on the meaning of the word time. In similar fashion, one could say Without Space, all things happen on top of each other! And again the meaning of on top of depends on the meaning of space. Finally, if we follow relativity, the real question becomes What is space-time? 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 | --- -- I was gratified to be able to answer promptly, and I did. I said I didn't know. -- Mark Twain
Re: What's sum of series of increasing powers?
Help! I'm working on an Excel spreadsheet and need a formula or function that will give, for an input A and B, the sum of all the powers of A for integers from 1 to B. Example: 1.05 + 1.05 squared + 1.05 cubed ... Can anyone help me? -- Tad Dunne This is called the geometric series, if you wish to look it up in a math book. For the series 1 + r + r^2 + r^3 + ... + r^(n-1) the formula is (1 - r^n)/(1 - r) If you take n to be infinite the formula becomes 1 / (1 - r) But! It only converges for -1 r 1. 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 | --- -- See when the Government spends money, it creates jobs; whereas when money is left in the hands of Taxpayers, God only knows what they do with it. Bake it into pies probably. Anything to avoid creating jobs. -- Dave Barry
Re: length of a spiral line
Does anyone know how to figure the length of a spiral line, given only the width between the lines and the diameter. or the radii of the circle I think this is underspecified; what spiral? Do you have a formula for the curve? Jim === He who wonders discovers that this in itself is wonder. -- M. C. Escher
