NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Astronomical Algorithms C++ source code
From: Frank Reed CT
Date: 2006 Dec 12, 16:31 EST
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From: Frank Reed CT
Date: 2006 Dec 12, 16:31 EST
"A collection
of freeware C++ classes which provide an implementation of the algorithms as
presented in the book "Astronomical Algorithms" (2nd Edition) "
I just want
to mention again that this *may be* the long way around to do
this sort of thing in the year 2006. The JPL ephemeris data, the result of
extraordinarily detailed and accurate numerical integrations, can easily be
stored at one arcsecond accuracy in 40 kilobytes per year of data, maybe less if
you put your mind to it. The only code you need to access it is trivial
interpolation code. You need actual data only at one or two hour
intervals for the Moon, once a day for Jupiter, etc. The cost to cover
longer periods of time is strictly linear and the accuracy (at least from the
point of view of ephemeris time) remains the same for thousands of years. This
is not the case with algorithmic approximations to the orbits such as those
published by Jean Meeus or the VSOP87 files. And by the way, the official
Nautical Almanac also uses the direct JPL ephemeris.
Note that the
above only applies to Solar System objects. You'll still want to apply
precession, nutation, aberration, parallax, and proper motion to the stars
themselves in code. Fortunately, that's not a big job.
Of course,
there's nothing intrinsically wrong with using algorithms, like those published
by Meeus. If you are coding for a device where storage space is in very short
supply and you intend to cover more than fifty years of data, then algorithms
like those will probably save you some storage.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
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