Hi Piers, I like the Noon and EoT Calculator and to my opinion to calculate sundials it is accurate enough.
I myself prefer a calculation of the EoT for a year in the middle of a leap-year's period and not an average table. With these values I would calcualte my EoT graphs on a sundial. For example 2002 or 2050. To find the correct North South line however I need a table for the year I am in. So to me the best would be the user can choose the year he wants. The year it realy is and a year for the calculations of the dial. The last one I would choose some 10 or 20 or 50 years ahaed. In that period the dial will give ( theoretical ) better readings from year to year. And another 10 or 20 or 50 years the accuracy hardly will decrease. And I can't enjoy my sundial for so many years I think...... A rather quick running method to calculate such a tabel is the method I use in my program equadecl. It calculates a formula for just one year and that formula is used 365 or 366 times for the table. The accuracy of the EoT is within 5 seconds of time. Also incorporate the change in the date at different longitudes. At Greenwich 00:00 it is 1 may, but at longitude 90 degrees East is is already 1.25 may. So the relation between the date and the EoT isn't constant all over the world. ( I didn't program this in equadecl; in that program only the values for noon at Greenwich are calculated ) Best wishes, Fer. Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <sundial@rrz.uni-koeln.de> Sent: Monday, May 07, 2001 1:25 PM Subject: Solar Noon and Standard Time Correction Calculator + 2 questions > is has now been posted on www.solar-noon.com > > There are two areas where further improvement may be possible, and I > would welcome the views of others. > > 1. We have used the average values as in Waugh (and repeated in many > other places). (You can get a printout of these values by setting the > longitude to zero.) Average values are good enough for the Spot- > On Sundial, for which this calculator was designed, and have the practical > advantage that the table can be kept next to the sundial without reprinting > it each year. But it would be better to provide more accurate values if this > can be done without too much additional complication. > > Question: would it be useful to the wider sundial community to have a > facility for calculations on the actual values for this year? Would it > be useful to anybody to have the whole year's figures on one sheet for > just this one year (and have to print out another one next year). > > 2. If we do use an average, are the Waugh figures the best ones to use. > We had previously checked them against the arithmetic average of the > NASS Diallist results for the first of each month over the 4-year cycle, > and there are differences ranging from 2 to 20 seconds. I am no > astronomer, and so really do not know what can or should be done about > this. > > Question: Can anyone suggest a better set of averages, or way of > calculating them? > > Comments gratefully received, and again many thanks for all the comments on > the original posting. > > Piers Nicholson >
