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Version 2.1.2 of my SofaJpl positional astronomy toolbox for the Windows
.NET Framework has just been released. It is a set of DLLs an
application can call, not an application itself. This release fixes bugs
and implements a long term ∆T model recently published. It's backward
compatible with any 2.x SofaJpl version.

http://home.earthlink.net/~s543t-24dst/SofaJpl_NET/index.html

A programmer's installation occupies almost exactly 1 megabyte. However,
that doesn't include any JPL solar system ephemeris files. Size is
smaller if SofaJpl is included as part of a software product, since some
files are needed only during programming.

C#, C++, and Visual Basic source code for a demonstration program is
online at the site. You need the Visual Studio software development
environment to run the program. The free "Community" version should be
sufficient. (I use the old free version, Visual Studio Express 2013,
probably no longer available.)

The demonstration program has a rudimentary user interface — to change
time, observer location, or identity of the body you must modify the
code — but it generates most of the frequently needed positional data,
and it's accurate. If the accuracy setting is increased to one
millisecond of arc, the precise reductions to apparent place in The
Astronomical Almanac are duplicated within one digit in the last place.

Angle display formats of D, DM, and DMS are available. Two lines of code
control the precision and format of the whole program. Time display
automatically adjusts to a precision commensurate with the angles.

The method in the demonstration program is not the only way to
accomplish that. My Lunar4 program has selectable precision and format
too, but uses a completely different method.

Speaking of Lunar4, the download on its page has been updated to include
the latest SofaJpl release. This is an interim update; I have more plans
for Lunar4.

To demonstrate the demonstration program, I present these predictions
for the equinox on September 23. (The second line is the formal
definition of the equinox.)

01:53:51 UTC  0 declination
01:54:06 UTC  180° ecliptic longitude
01:54:08 UTC  12 h right ascension
01:54:13 UTC  0 geodetic (ITRS) latitude

(DE422 ephemeris, IAU 2006 precession and 2000B nutation models, and
predicted polar motion X = 0.2052", Y = 0.3394". Delta T is irrelevant
here because none of the coordinates is affected by Earth rotation.)

Note that JPL's Horizons online calculator won't exactly agree with all
my numbers, mainly due to a different precession / nutation model.

   

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