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    Astronomy DLL for .NET: SofaJpl 2.1.2 released
    From: Paul Hirose
    Date: 2018 Aug 29, 16:44 -0700

    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.
    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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