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
