NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Computer generated Almanac
From: Dan Allen
Date: 2003 Sep 5, 08:54 -0700
From: Dan Allen
Date: 2003 Sep 5, 08:54 -0700
On Friday, September 5, 2003, at 06:36 AM, Vic Fraenckel wrote:
> Loath as SOME users of this list are to introducing computers into
> celestial
> navigation, I would like to find someone that has used the "JPL
> Planetary
> and Lunar Ephemerides" data to actually produce a computer almanac. I
> would
> like to do so but am not sure how to proceed. I am NOT interested in
> getting
> the data via the many excellent Web based systems as accessing the web
> is
> NOT practical while at sea.
>
> Any enlightenment will be appreciated.
I got that CD-ROM years ago and found it hard to figure out how to use
it. The data files on the CD-ROM are huge and are of the highest
accuracy. Source code for a FORTRAN program is on the CD and other
people have since made C versions, but I am still at a loss as to how
to use it all. I confess I have spent little time on the project, but
it is not very user friendly.
The simplest way of producing a computer almanac is to code up the
algorithms given in Jean Meeus' "Astronomical Algorithms" book. I have
done this for the sun in the Awk programming language and it is found
on my web site at:
http://home.comcast.net/~danallen46/AwkS2K.htm
Awk is a very plain and simple language in the spirit of the C
programming language, and this one page of code could easily be
translated into C, Perl, Python, Java, or whatever. You are free to
use it as a basis for your own almanac.
Dan
