Paolo GREGORIO wrote: > > Angelo Brazzi wrote: > > > > I have to calculate a large orizzontal sundial (8-10 m stylus) and I need > > to know how to > > calculate, with a good accuracy, the sun declination for April 18 1693. The > > formulae reported by > > the sources that I have go back to 1900 but not further. Can anyone help > > me? > > Thanks. > > I found out about sundials mailing list from Sundials on the Internet. > > > > Angelo Brazzi > > Dear Angelo, > > I have read your mail and the answers, all founded on Dialist > Companion program; I have also tried the formulation given by > T.C.Van Flandern and K.F.Pulkkinen in "Low Precision Formulas > for Paletary Positions", where "Low Precision" stands for "one > minute of arc", valid for the date range 1950±300 years. > > The result of computation for April 18, 1693 (0h ET) is > > RA = 1h 35m 06s > Decl = 9° 55' 59" > R = 1.004931 > > Furthermore, the authors note that "for more remote dates, within > historical times, it is necessary to take the expression for the > fundamental > arguments (Exp.Supp. 1973) with greater precision, and in some cases > to include secular effects as well (Brouwer and von Woerkom, 1950). > > With the best > regards, > > Paolo > Gregorio
To all who try to calculate the declination of 1693-04-18. I now used the following programs to calculate this value and all the answers do agree well. Dialist Companion 11.161565 degrees Solar 11.1619 " Planets 11.1619 " Solar is a program made in 1988 by J. Theunisz. Planets is a program made by Jean Meeus, the author of the book Astronomical Algorithms. I myself can't control the accuracy of all the programs, but the answers are all the same. Fer J. de Vries Netherlands.
