Re: a dialist's paradise
At 02:58 PM 7/17/99 EDT, [EMAIL PROTECTED] wrote: Don't gripe about Daylight savings time. A truly inspired dialist would invent a dial that would work with either. This is not an inspirational invention but a practical technique. One way to show both ST and DST is to mark the numbers for the hours on the solstice declination lines. When the declination is negative (fall and winter) read standard times. When the declination is positive (spring and summer) read the daylight savings times. This works reasonably well with the switch between standard and daylight savings time being near the equinoxes. You should also build in the longitude correction and an analemma for the eqt correction. Then anyone using the dial could check their watch and comment that the dial was showing the correct time. We all know better. The clocks are wrong. Where I live the clocks try to tell me that it is 1:40 in the afternoon when the sun is due south and at its highest altitude. Ridiculous. Everyone knows that this time is high noon. However I do use clock time when I am headed to the airport to catch a flight. Roger Bailey Walking Shadow Designs N 51 W 115
Re: A Tough One?
Mike Cowham wrote: Dear Friends, I have a vertical east declining sundial that I believe was once fixed to a church building. Its gnomon is missing. What I wish to calculate is the latitude of the dial, and its declination. I am sure that it is a very easy problem to solve, but so far I have failed. When I have this information, I hope to be able to locate its original site, (I already have a rough idea of the area of England), and maybe find some evidence of where it was fixed to the building. The only real clue to its location is given by the angles made by its hour lines - assuming them to be accurate. Thanks in advance to anyone who may be able to help. Regards, Mike Cowham. Cambridge, England. Dear Mike, Here I give just a number of formulae by which the latitude phi and the declination d of a vertical sundial can be calculated, assuming the pattern is well drawn. Measure the angles of the following 2 hourlines : - for east decliner : hour 6 and 9 - for west decliner : hour 18 and 15 Name these angles t45 and t90 and use positive signs for the angles. Calculate : P = cot(t45) - cot(t90) Q = cot(t90) X = P*P Y = Q*Q a = Y b = X + Y - 1 c= -1 Z = (-b + sqrt(b.b - 4.a.c)) / (2.a) or Z = (-b - sqrt(b.b - 4.a.c)) / (2.a) Take the positive answer for Z Then phi = atn(1/sqrt(Z)) d = asin(Q/tan(phi)) ( sqrt is square root out of... ) Example : t45 = 29 degrees t90 = 68.78 degrees X = 2.0044 Y = 0,1508 a = 0,1508 b = 1.1552 c = -1 ( of course ) Z = 0,7852 phi = 48.4552 degrees d = 20.1244 degrees ( east or west ) I hope I didn't make any typing error. Otherwise have a look in bulletin of De Zonnewijzerkring, 88.3, page 31. Best wishes, Fer. -- Fer J. de Vries [EMAIL PROTECTED] http://www.iaehv.nl/users/ferdv/ lat. 51:30 Nlong. 5:30 E
R: Design at its worst
-Messaggio Originale- Da: The Shaws A: Mailinglist Sundial Data invio: domenica 18 luglio 1999 15.48 Oggetto: Design at its worst I was down in my local garden centre yesterday, and saw THE most ridiculous attempt at a sundial I have EVER seen in my life... I have no problem in believe that. I would like to tell you what I read some two years ago looking for sundials in Altavista. I tried to look in news lists and I found a Garden's lover list, many subscribers ask to others how to fit the just bough horizontal sundial in the right position inside the garden (my God sellers should know), than I found many answers to them (no one correct), but the most surprising one was: «Why you get in problem for this? You surely will never go more than the first two days in your garden to look at the sundial, you will prefer to look at your watch. So don't be afraid fix it as you better like, surely it will look fine the same in your garden.» Since people will think in this way, everything could happen. Mario - Mario Arnaldi Viale Leonardo, 82 48020 LIDO ADRIANO - Ravenna Italy E-Mail [EMAIL PROTECTED] -
Question about annual amount of sunlight
Hello dialists, I read Marilyn Vos Savant's (the person with the highest measured IQ) column this morning, and found an interesting question and response which I'm not sure is correct. To paraphrase: The question was, Over the span of a year do all places on earth recieve on average exactly 12 hours of daylight and 12 hours of night. Marilyn's response was that indeed this was the case. Incidently I suspect her response is wrong because of the fact that the Earth's orbital speed is different during different times of the year giving the north hemisphere a slightly longer summer. Anyway, I'd like to hear what others think. Troy
Design at its worst
Re: a dialist's paradise
Re: The great jet experiment
John Bercovitz wrote: What have I proven? The jet reaction is real, and measures as predicted, but seems to have nothing to do with the Moss effect. The Moss effect must depend on the configuration of the spray coming out of the nozzle. Also shown was that in this case, the flow around the nozzle while it was in the bucket was not a part of this problem. Indeed, the water in the bucket looked completely turbulent. The effect is real enough and others have repeated it elsewhere. In hindsight I'm glad I was quite specific in describing the water 'jet' in my experiments. viz/ a tightly-concentrated stream of droplets rather than a 'solid' stream of water as John seems to have isolated this as a possible 'culprit'. The Moss Effect! ... fame at last! :-) ...move over Henri Coanda!.. but he's another story ;-) With apologies to any who have found this off-topic thread tedious. Tony Moss
