In article ,
"W. eWatson" wrote:

Greg Neill wrote:

snip

Duffett-Smith:
- Practical Astronomy With Your Calculator
- Astronomy With Your Personal Computer

Meeus:
- Astronomical Formulae for Calculators
- Astronomical Algorithms

Duffet-Smith's computer book contains a lot of BASIC program
listings, which may or may not be of use to you. Meeus' book
has a disk available containing the data and programs, but the
methods in the book are presented in mathematical form that is
not just pidgin BASIC.


Practical Astronomy With Your Calculator, 2nd ed. Never heard of it
until last week. I'm using a library based on their work. I suspect that
it may be used because the copyright expired, or they really had no
objection to others using it.

Astronomical Formulae for Calculators, 4th ed. I have it.

That's been pretty thoroughly superseded by _Astronomical Algorithms_.
Most of the material was taken up into the latter book, but updated
throughout from the 1900-epoch methods to J2000-based ones, and in some
areas much expanded, the _AFC_ procedure being given as a short or
approximate alternative to a new one that's more elaborate but also more
accurate. The high-precision planetary-position calculations in _AA_
involve dozens of periodic perturbation terms, the listing of whose
coefficients for all the planets makes a forty-page appendix.

I wonder what the pros use, if not these? I suspect some of the better
math libraries are involved in any case.

I'll stick with Duffett-Smith. In any case, Meeus is helpful checking
what I'm doing with the library and providing a reference for what's
really happening. The library has virtually no introductory material.
Maybe Duffett-Smith provides the background.

I don't have his PC book. The Calculator book does provide the rationale
for most of its methods -- at least a sketch of the derivation, and
helpful diagrams -- which are also well illustrated with step-by-step
examples. I think it's fair to say Meeus assumes more background on the
reader's part, and discusses practical considerations in more detail:
under what circumstances to apply corrections or in what order, how the
precision degrades with distance in time from the reference, and so on.

One aspect of _PAWYC_ (I have the 3rd ed., 1988) that stands out as
unique is a method it presents (beside the traditional spherical-trig
formulae) that uses matrices for generalized coordinate transformations,
including precession.

--
Odysseus