RE: A blunder on the astronomical clock in Prague
Willy, Thank you for starting this interesting discussion and for directing us to your website with its marvellous coverage of the Prague clock. It prompted me to consult Henry King's book entitled Geared to the Stars which deals among other things with astronomical clocks. He seems to have thoroughly investigated the mechanism of the Prague clock and here is what he wrote in 1978 about the clockwork as it was in 1865: The horizontal input arbor ended in a long lantern pinion of 24 teeth. This rotated 15.25 times in 24 hours and meshed with three concentric wheels 1.14m in diameter and provided with 365 teeth(zodiac), 366(sun) and 379(moon). In 24 mean solar hours, 24x61/4 or 366 teeth of the pinion rotated the sun-wheel once while the zodiac-wheel advanced one tooth and the moon wheel slipped back 13 teeth. He continues as follows: The three large concentric wheels...still form part of the dialwork, but they are no longer turned by a simple pinion and the moon-wheel has a correcting mechanism added by Boehm in 1865. This suggests to me that the original clockwork turned the sun-wheel at a regular rate to match the mean sun and there is no record of a subsequent equation of time modification since I find it hard to believe that such a modification would have escaped the notice of Henry King. This evidence makes me think that Frank King is correct in his guess. Geoff Thurston _ From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Frank King Sent: 28 February 2011 07:54 To: Willy Leenders Cc: Sundial sundiallist Subject: Re: A blunder on the astronomical clock in Prague Dear Willy, I am not very familiar with the Prague clock and I am confused by the recent messages. You say: ... the clock indicates now Central European Time rather than solar time as it once was... This suggests something far more radical than simply setting the clock for the wrong longitude to keep the tourists happy. If I interpret you literally, you seem to be saying two conflicting things about the mechanism at the heart of the clock: NOW: the clock indicates Central European Time - this suggests exactly 24 common hours each day (albeit set for the wrong longitude). IN FORMER TIMES: the clock indicated local sun time - this suggests that there were NOT exactly 24 common hours each day because sun time is not quite in step with common hours. QUESTION Did the clock really indicate local sun time before it was adapted to keep tourists happy? If the answer is yes, that means the clock mechanism used to take account of the Equation of Time AND that this mechanism has now been disconnected. Can this be true? My guess is that the clock used to indicate local MEAN sun time but I should like to have that guess confirmed or rejected! Frank H. King Cambridge, UK --- https://lists.uni-koeln.de/mailman/listinfo/sundial _ No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1204 / Virus Database: 1435/3471 - Release Date: 02/27/11 --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Another Sundial with VI at Midday...
Dear Frank, I have only just got around to reading your account of the Margaret Stanier Memorial Dial which I downloaded a couple of weeks ago so I hope you will treat this response as better late than never. Congratulations on implementing a novel dialling concept in such a beautiful dial. Your account of the evolution and manufacture of the dial was a delight to read and I am surprised that it has not resulted in more widespread acclaim from this list. I must assume that your readers are dumbfounded. My only comment is that your omission of the sunrise/sunset hours should be regarded as of no practical disadvantage since the timings of these phenomena are evident to the observer without the need for a dial. You asked to be alerted to typos and I think that you might have transposed the standard deviation values for R1 and R2 in the last sentence of the penultimate paragraph on page 30. Thank you for providing us with such a comprehensive and thought-provoking account of your creation. Best Wishes, Geoff -Original Message- From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Frank King Sent: 26 September 2010 17:18 To: sundial Subject: Another Sundial with VI at Midday... Dear All, The beer-glass sundial spotted by Mike Cowham brought on a panic attack. More strictly, it was his comment that caused alarm... The glass acts as the gnomon but the real horror ... midday was at VI. Maybe every reader should pour a glass of beer (or something stronger) before reading any further. I have just inaugurated my latest creation and, guess what, midday is at VI. Should I spend my declining years designing sundials for garden centres? Make sure you have a first-aider to hand and take a look at: http://www.cl.cam.ac.uk/users/fhk1/Newnham/FHK+Dial.jpg I hope, by the way, that you like my outfit. I chose to wear British Sundial Society-approved colour-coordinated yellow for the occasion. This sundial is a memorial tribute, by Newnham College, Cambridge, to Margaret Stanier, lately Editor of the BSS Bulletin. About 10 years ago, Margaret told me how important mass dials were so I thought I would come up with a design which is (ever so loosely) based on a 24-line mass dial. My goal was impossible but I am not easily put off... I wanted an unequal-hours sundial where the time is indicated by the direction of the shadow of a rod gnomon. [I didn't want to use a nodus and its point-indicating shadow.] Is there a best approximation? Newnham College asked for a account written for technically-minded academics who know nothing about sundials. You can see this, and numerous photographs, at: http://www.cl.cam.ac.uk/users/fhk1/Newnham/write-up.pdf You will even see that this dial incorporates a few dialling jokes :-) Here I proffer some acknowledgements to: Margaret Stanier for the inspiration. Frans Maes and many others for making me think about the Braunschweig dials. Geoff Thurston for making me think about just what is meant by best-fit when making compromises. Gianni Ferrari for explaining that the hour-lines on this design don't have great gnomonic meaning. Not many unequal-hours sundials get made these days so, if you think it is a sundial at all, make the most of this one :-) Please let me know of all the typos that you spot. I haven't handed the account to the College yet! Now what was that beer that Mike was telling us about? Frank H. King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Sundial compass on eBay
Roger, Bob and Brooke, Thanks for your kind advice. I have just checked the LHA adjuster knob and, unfortunately, there is no sign of any potential in-out movement. I did as suggested by Bob and Brooke and bought some penetrating oil which has loosened up the mechanism but I think I shall need to strip and regrease it to make it silky smooth. I am still hoping that somebody might have an exploded diagram before I venture into the unknown. Geoff -Original Message- From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Roger W. Sinnott Sent: 04 July 2009 17:44 To: 'Sundials' Subject: Re: Sundial compass on eBay Geoff (and others), Sorry about the accidental blank message just sent. I have an AstroCompass (but not readily accessible at the moment). If I remember correctly, one main knob (possibly the LHA mechanism you mention) operated very stiffly until I PUSHED IN ON THIS KNOB. It is spring loaded to prevent turning by mistake. -- Roger - Original Message - From: Roger W. Sinnott rsinn...@post.harvard.edu To: thurs...@hornbeams.com; 'Peter Mayer' peter.ma...@adelaide.edu.au; 'Sundials' sund...@rrz.uni-koeln.de Sent: Saturday, July 04, 2009 12:34 PM Subject: Re: Sundial compass on eBay - Original Message - From: The Thurstons thurs...@hornbeams.com To: 'Peter Mayer' peter.ma...@adelaide.edu.au; 'Sundials' sund...@rrz.uni-koeln.de Sent: Friday, July 03, 2009 12:45 PM Subject: RE: Sundial compass on eBay Folks, Alerted by Peter's message below, I have just bought an ex-Air Ministry Astro Compass MkII from eBay. I have wanted one of these for a while so thanks to Peter for posting about it. The instrument seems to be in pretty good condition but the LHA mechanism is stiff to turn and I am wondering about attempting to free it. Before I blunder in, I should be grateful for any advice on: - what lies inside the LHA mechanism - whether I can just apply some WD-40 and hope it finds its way to the critical parts - whether I could disassemble it with any hope of putting it back together Best Wishes, Geoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Sundial compass on eBay
Folks, Alerted by Peter's message below, I have just bought an ex-Air Ministry Astro Compass MkII from eBay. I have wanted one of these for a while so thanks to Peter for posting about it. The instrument seems to be in pretty good condition but the LHA mechanism is stiff to turn and I am wondering about attempting to free it. Before I blunder in, I should be grateful for any advice on: - what lies inside the LHA mechanism - whether I can just apply some WD-40 and hope it finds its way to the critical parts - whether I could disassemble it with any hope of putting it back together Best Wishes, Geoff -Original Message- From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Peter Mayer Sent: 23 June 2009 10:33 To: Sundials Subject: Sundial compass on eBay Hi, There's an interesting-looking RAF sun compass for sale on EBay: Collectables Militaria World War II (1939-1945) RAF best wishes, Peter -- Peter Mayer Politics Department The University of Adelaide, AUSTRALIA 5005 Ph: +61 8 8303 5606 Fax : +61 8 8303 3443 e-mail: peter.ma...@adelaide.edu.au CRICOS Provider Number 00123M --- This email message is intended only for the addressee(s) and contains information that may be confidential and/or copyright. If you are not the intended recipient please notify the sender by reply email and immediately delete this email. Use, disclosure or reproduction of this email by anyone other than the intended recipient(s) is strictly prohibited. No representation is made that this email or any attachments are free of viruses. Virus scanning is recommended and is the responsibility of the recipient. --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Experimental Method for Earth Radius
It is interesting to extend Fritz's calculations to t=120 sec when A=0.5 deg and H=804 ft. Assuming that the diameter of the sun is 0.5 deg, this indicates the extent of the sun's penumbra so that any portion of the building above 804 ft in the original problem would be fully illuminated as the green flash is observed from ground level. This suggests that the very gradual transition from light to shadow would make the proposed method impracticable. However, the timing of the green flash or more probably the disappearance of the upper limb of the sun by two vertically-separated observers should work. This would be an excellent school project for the International Year of Astronomy. Geoff -Original Message- From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Fritz Stumpges Sent: 04 March 2009 18:34 To: f.w.m...@rug.nl; JOHN DAVIS Cc: sundial@uni-koeln.de Subject: RE: Experimental Method for Earth Radius Hi All, I apologize if someone has already answered this thread, here or in previous posts; and even more if it has nothing to do with the green flash and seeing it again on another floor a short time later. I think that one way to see it is that the earth is turning at an approximately constant 15 degrees per hour, or A degrees / T time. The shadow going up the building will be rising up in relation to the cosine of this angle. For simplicity all of this has to be imagined at the equator, because at the poles the sun might not be rising or setting. Imagine two lines, R, coming from the center of the earth, one follows or stays with the sun's point of tangency, the other line stays at the building and grows H in height. The formula is simple: R/(R+H)=cosA OR H=(R-R*CosA)/cosA Where R = 4,000 miles (approx at equator) or 21,120,000 ft and A deg = T sec * .00416667, (15deg/hr) Then at T = 60 sec; A=.250deg and H = 201ft 30 sec; A=.125deg and H = 50ft 10 sec; A=.041deg and H = 5.6ft So it does seem that someone could climb a 5 story, 50 ft building in 30 seconds and see the green flash again (or still). I wonder if one were in a programmed glass elevator at the beach and it started up at the right speed in a 20 floor building, you could watch the same green flash for 1 minute! I hope I'm not way off on this thread or calculations, I'm supposed to be working!! Fritz -Original Message- From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de]on Behalf Of Frans W. Maes Sent: Wednesday, March 04, 2009 1:00 AM To: JOHN DAVIS Cc: sundial@uni-koeln.de Subject: Re: Experimental Method for Earth Radius Dear John all, Imagine a building on a west-coast seaside resort. As the sun sets, the terminator (the shadow of the horizon) creeps slowly up its wall. It takes only two lines of elementary geometry to proof that the height of the shadow increses with the SQUARE of the time. Mathematically expressed: the terminator travels up at a constant acceleration. That is the basic idea behind David Bowman's procedure quoted in John Davis' posting. So far, so good; if not brilliant! What I find counter-intuitive, though, is the following. Standing beside the building, we see the sun disappearing behind the horizon at a CONSTANT rate. On the other hand, if we would want to keep the last sliver of sun in sight, we would have to climb the building's stairs at an ever INCREASING rate. So, where is my intuition led astray? Best regards, Frans Maes JOHN DAVIS wrote: Dear Dialling Colleagues, I'm forwarding this message from another mailing list as I believe it may be of interest to all sun-watchers. Mathematicians amongst you might like to work out the details of the 'fudge factor'. Regards, John --- Dr J Davis Flowton Dials --- On *Sun, 1/3/09, Brian Whatcott /betw...@sbcglobal.net/* wrote: From: Brian Whatcott betw...@sbcglobal.net Subject: [rete] Experimental Method for Earth Radius To: sexta...@yahoogroups.com, r...@maillist.ox.ac.uk Date: Sunday, 1 March, 2009, 4:38 AM I am relaying this note from a physics teachers list, believing it may be of interest to you. For me, it carried the same kind of frisson as reading about Harrison's stellar transit method for timing chronometers. Brian W David Bowman wrote: I've come up with a fairly simple means of measuring/calculating the size of the earth using only local measurements (not requiring multiple sightings at far away locations like Eratothenes' method needs). The idea is to observe and time the motion of the terminator at sunset/sunrise ascending or descending the face of a building, pole, or other tall structure with an exposed vertical face. It is a fairly simple exercize in trigonometry to realize that if one is situated on the equator during an equinox that the terminator ascends
RE: Vertical South dial with horizontal gnomon
Keith, The formula from Waugh should work fine but only for a dial with the gnomon aligned to the rotation axis of the earth ie pointing approximately to the pole star. I do not think that you can use a horizontal gnomon with a vertical dial to record the passage of modern hours. However, you might consider using a nodus supported by a horizontal rod as indicated in the attached diagram. You could then tell the time using the shadow of the nodus rather than the shadow of the rod. The nodus must be placed so that it falls on the edge of the imaginary gnomon which it replaces. Geoff Thurston N51D18 W0D55 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Keith E. Brandt, WD9GET Sent: 10 September 2008 05:04 To: [EMAIL PROTECTED] Subject: Vertical South dial with horizontal gnomon Sunny friends, X-Forwarded-for: [EMAIL PROTECTED] by Tucows For various reasons, I'm wanting to build a rather different dial. The plan is for a south-facing vertical dial, but I want to design it with a horizontal gnomon. Waugh states that a vertical south-facing dial has the same hour lines as a horizontal dial at the colatitude. Therefore, to calculate the positions of the hour lines, I used the following formula in Excel: =90-(180/PI())*ATAN((TAN(L8*PI()/180)*SIN(Colatitude*PI()/180))) With L8 being the angle of the sun from noon, calculated by [number of minutes from noon] * (15/60). What needs to be changed to make this work properly with a horizontal gnomon? Keith -- Col Keith E. Brandt, MD, MPH USAF-NASA Aerospace Medicine Liaison Officer Johnson Space Center, Houston, Texas /[EMAIL PROTECTED]// Goodbye cruel world that was my home- there's cleaner space out here to roam Put my feet up on the moons of Mars- sit back, relax, and count the stars /*This message transmitted with 100% recycled electrons --- https://lists.uni-koeln.de/mailman/listinfo/sundial Gnomon vs Nodus.pdf Description: Adobe PDF document --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Braunschweig: Another Dial and a Puzzle
Dear Frank, Thank you for your thought-provoking proposal. I have been meaning to study temporary hours more closely and you gave me a reason to do so. I thought that I had better test my understanding by tackling your puzzles before I ventured any comment on your improved dial. So here goes.. I started off by calculating the hour angle by which the semi-day exceeds 90 degrees using the formula: sin (epsilon)= tan (lat)x tan(dec). I then plotted this for a range of declinations from -23 to +23 degrees for latitude 52.25N. This exhibited the s-shape but I also plotted it for 66N to make the s-shape more pronounced. The thing to note about these curves is that they are symmetrical about the eqinoctial point for any pair of +/- declinations as we would expect from the formula above. Therefore any great circle drawn through an eqinoctial point and the corresponding summer solstitial point must pass through the winter solstitial point as well. The great circle defined by the 3 points will be unique and its plane will pass through the centre of the celestial sphere, where our nodus is located. Thus the great circle will define a shadow plane which will project into a straight line on any plane surface. My diagrams show the hour lines to the east of the meridian only but, of course, they also appear in mirror image to the west of the meridian. Because of their symmetry about the meridian, any corresponding pair of hour lines will if extended meet on the meridian. I hope this reasoning is sound because I am beginning to think that I understand the problem. One thought occurs to me when looking at the s-curves. The line joining the solstitial points gives a zero mean error over the year but it should be possible to find a better overall fit by joining for example +/-15 degrees by a straight line. What do you think? Geoff Thurston N51D18 W0D55 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Frank King Sent: 04 September 2008 09:46 To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; Gianni Ferrari; sundial Subject: Braunschweig: Another Dial and a Puzzle Dear Frans, Roger, Karlheinz, Gianni et al, Braunschweig is fascinating and I have a new design to offer. See: http://www.cl.cam.ac.uk/users/fhk1/BraunschweigV.pdf and I have an associated puzzle for anyone who enjoys spherical geometry. See below! First, some history... THE SIMPLE CASE Frans, citing Zinner, said: The usual medieval sundial was vertical and semi-circular, with 12 (equally spaced) temporal hour lines. A perpendicular gnomon was inserted into the center, where all lines intersect. This kind of sundial has an orthogonal gnomon and a set of 13 lines (I include 0 and 12) at 15-degree intervals. Even on a direct south-facing wall this will not indicate temporary hours very accurately. Gianni has quantified the errors. AN IMPROVEMENT An obvious improvement is to vary the spacing so that the hour lines are correct at the equinoxes. The 1334 Braunschweig dial seems to be an example. Roger supplied the angles from the brochure Die Sonnenuhren am Braunschweiger Dom. Gianni has another paper confirming that the lines on this dial closely follow this spacing (though he uses the date 1350). Roger is a little harsh: The early dial at Braunschweig, perhaps 1334, is similar to the early mass dials... These represent a crude understanding of time... Though he acknowledges: There is a moderate improvement at Braunschweig as the angles ... represent the timelines at the equinox... THE IDEAL Mathematically exact temporary hour lines are not straight so you cannot use a gnomon (a style which casts a *line* shadow). You have to use a nodus (which casts a *point* shadow). Running from the summer solstice point to the winter solstice point, the line for a given temporary hour forms a narrow S-shape. If you draw the straight line from the summer solstice point to the winter solstice point you divide the S as in a $-sign. Here is the... PUZZLE Show that the straight line from the summer solstice point to the winter solstice point passes through the equinoctial point but through no other point on the S-shape. A DIFFERENT IMPROVEMENT Noting that summer, equinoctial and winter points are collinear, another obvious step is to use the straight lines through these triplets as approximations to the true temporary hour lines. Unfortunately these straight lines do not intersect at a common point but we can proceed as follows: 1. Take a vertical direct south-facing wall. 2. Set up a nodus as just described. 3. Mark the points for the temporary hours along the winter and summer hyperbolas and along the equinoctial line. 4. Note that, for a given hour, the three points in a triplet are collinear. 5. Take a particular pair of straight lines: the line through the 3h triplet and the line through the 9h triplet. 6. Note that these two lines
RE: Easter
Frank, The Ecclesiastical Calendar is a wonderful book and absolutely essential for anyone with an unhealthy interest in the labyrinthine workings of the church calendar. It was written by the Bishop of Meath during his spare time and describes in complete detail the development and theoretical foundations of the ecclesiastical calendar. Unfortunately, it is difficult to find and I have not seen a copy offered for sale but I did manage to borrow a copy from the British Library which I returned with great reluctance. Google Books have scanned a copy of the book and its description can be found at: http://books.google.com/books?id=qbA-rzFsIoMC but it cannot be downloaded in UK - apparently for copyright reasons although this seems highly conservative as the author died before publication in 1877. However, anyone accessing Google Books from the US may download a high-quality PDF copy of the book and I strongly recommend them to do so. Geoff -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Frank King Sent: 16 March 2008 21:43 To: Mac Oglesby Cc: sundial@uni-koeln.de Subject: Re: Easter Dear Mac, Many thanks for your message... If you can find the time, this mailing list member ... would much appreciate details about how you derived the list of dates. I am glad you asked this question and equally glad that Patrick Powers has supplied the algorithm! I had it in my head that this algorithm was first published in Butcher's Ecclesiastical Handbook in 1876 and I give this as the (incorrect) citation in one of my sets of student exercises. When I Googled Butcher's Ecclesiastical Handbook all I got was a couple of references to plagiarised versions of my exercises. Tee hee! I wouldn't have discovered my error had you not prompted me to look for something else! I first saw the algorithm in Meeus and now see that he gives the correct citation Butcher's Ecclesiastical Calendar, 1876. There is a reasonably complete account in: http://en.wikipedia.org/wiki/Computus One of my favourite books is Calendrical Calculations by Edward M. Reingold and Nachum Dershowitz. It is full of good jokes! This book almost attributes the algorithm to Clavius and Lilius (key figures in the Gregorian reform of the calendar). Once you have implemented the algorithm you can then have fun determining the length of the cycle. A naive approach is to start at an arbitrary year and look for the next year that has Easter on the same date. You then look to see whether the two following years match too. They won't! So you look for the next matching year and keep going until you repeat indefinitely. Your program will take a long time!! Calendrical Calculations says: The dates of Easter repeat only after 5,700,000 years, the least common multiple of the 19-year Metonic cycle, the 400 years it takes for the Gregorian calendar to return to the same pattern of days of the week, the 4000 years it takes for the Gregorian leap-year corrections to add up to 30 days, and the 9375 years it takes for the correction to the Metonic cycle to amount to 30 days. If you get to understand the ecclesiastical moon and the ecclesiastical vernal equinox you will wonder whether the algorithm works at all. In fact it does a remarkably good job at predicting the first Sunday after the first full moon after the vernal equinox which is often given as the formal definition of Easter. What I should like to know is what is meant by Sunday! Sunday begins at different times in different places. Could it mean Sunday as it is timed at the longitude of Rome? Enough from me! Frank --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Urban Meridian
Jim, You certainly have a challenging location for your project. However, judging by the Microsoft VE imagery, there appears to be a gap in the buildings to the south west. I wonder if you could time the extinction of a star behind one of the adjacent buildings as observed from the location of the clock through the gap and thereby determine the bearing to the building edge. Armed with this knowledge and a theodolite you would then be able to orient the clock. It's an interesting problem and I hope you will let us know how you solve it. Geoff Thurston -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of James E. Morrison Sent: 28 December 2007 18:45 To: [EMAIL PROTECTED] Subject: Urban Meridian The nature of the problem is nicely shown with Google Earth. Go to 39 06N, 94 34 55W (the corner of 12th and Walnut in Kansas City). Set it for 3D buildings and rotate and tilt the view. The architect tried city maps, county maps, utility maps, etc. and they don't agree. A lot. Kansas City is a city that evolved and streets are pretty much where they ended up, without much in the way of long term planning. We haven't tried to get access to the tops of the buildings. I hadn't thought of doing that. We can't use Polaris from the park. A building is in the way. Jim James E. Morrison [EMAIL PROTECTED] Astrolabe web site at astrolabes.org --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Dialling Puzzle for Christmas Eve
Frank, The west-declining vertical dial on the side of my house has a gnomon shadow which shortens until about 1440hrs and then lengthens. A hasty (and therefore unreliable) calculation suggests that a vertical dial declining about 38 degs west of south in the latitude of Cambridge might experience its shortest shadow around 1500hrs. Now it's nearly time to switch on the radio for the carol service. Best wishes, Geoff Thurston 51D18N 00D54W -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Frank King Sent: 24 December 2007 13:43 To: Sundial List Subject: Dialling Puzzle for Christmas Eve Dear All, The BBC has been trailing their broadcast of the Christmas Eve Carol Service from King's College here in Cambridge with this introduction... At 3 o'clock, just as the shadows begin to lengthen,... My first thought was that shadows begin to lengthen immediately after 12 noon but, on thinking about it, I can see several ways to arrange for shadows to begin lengthening at exactly 3 o'clock. Would anyone else like to make some suggestions? As it happens, with just over an hour to go, it is 100% overcast here so this puzzle is rather academic! Happy Christmas Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Transit of Venus Calculation
John, Have a look at http://www.sil.si.edu/exhibitions/chasing-venus/pop_using.htm for a basic explanation of the principles involved. It does not explain that the relative distances of the earth and Venus from the sun are determined from a their measured orbital periods. Geoff Thurston -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of John Foad Sent: 24 April 2004 11:27 To: sundial@rrz.uni-koeln.de Subject: Transit of Venus Calculation Sorry if this is thought to be too far off the subject of sundials, but can anyone explain the principle of the calculations to determine the Sun's distance from the Transit data? As I understand it, the minimum you need is the time of (say, first internal contact) at two widely separated places. I would like to understand just the basic principle (without going in to all the complications of exactly where the two places are, different lat/long, curvature of the earth, and I am sure much much more). Leaving out the complications, I feel sure it must be possible to explain the underlying idea, but I have not found it in the few books I have tried. -- John Foad - -
RE: PowerPoint Setup
John Frans, Using Powerpoint 2000 I have an option to print out the notes alongside the slides at 3 to a page. Here is what I do: File/Send To/Microsoft Word/Notes next to slides Then simply print out the resulting Word document Geoff Thurston 5118N 0054W -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Frans W. Maes Sent: 29 March 2004 08:01 To: John Carmichael Cc: Sundial List Subject: Re: PowerPoint Setup Hi John, Don't print out 65 pages of paper prints, one for each slide. Instead, go to File - Print. Under Print what, choose Handouts. In the box Handouts, choose Slides per page: 3. Next to each slide you will get space to write your notes. Frans -
RE: Lost contact??
Tony, I believe the current address for Rete postings is: [EMAIL PROTECTED] Here is an extract from the administrative commands for the list: --- Administrative commands for the rete list --- I can handle administrative requests automatically. Please do not send them to the list address! Instead, send your message to the correct command address: For help and a description of available commands, send a message to: [EMAIL PROTECTED] To subscribe to the list, send a message to: [EMAIL PROTECTED] Geoff -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of tony moss Sent: 25 January 2004 12:58 To: Sundial Mail List Subject: Lost contact?? Fellow Shadow Watchers, I've recently been trying to place a query on the 'RETE' mailing list without success so it may be that my contact email address may be out of date. The address I have been using is: [EMAIL PROTECTED] Have I got it right? It is quite possible that the answer to my query may be known to someone on the SML so I have repeated it below: Thanks in anticipation, Tony Moss Hi all, A theodolite by Cooke, Troughton Simms with the Serial Number Y1749 recently came into my possession. This instrument was seemingly current in about 1930 and must then have been supplied with a handbook for use and maintenance which I would dearly love to have sight of as there are several features, possible modifications/repairs which puzzle me. Can anyone help with this please? Tony Moss Lindisfarne Sundials P.S. A jpeg to assist in identification is available if necessary. - -
