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On 2019-04-08 10:16, David Shoemaker wrote:
 > I've done several searches for SofaJPL and keep running into dead
ends - http://home.earthlink.net/~s543t-24dst/SofaJpl_NET/index.html for
example - page not found - does anybody have a working URL for SofaJPL ?

My site is down, reason unknown. Until I get it working again, contact
me by private email and I'll deliver the product as an attachment. To
quote the web page:

SofaJpl is a positional astronomy DLL to assist Windows .NET Framework
applications with computation of celestial body positions. In my tests,
the reduction to apparent place examples in The Astronomical Almanac are
duplicated within one digit in the last place. Because it complies with
the CLS (Common Language Specification), SofaJpl is equally accessible
from all .NET Framework languages. SofaJpl was developed primarily for
my personal use, but anyone may use it for free.

SofaJpl components:

• The International Astronomical Union SOFA Collection (SOFA release of
2017-04-20), "an accessible and authoritative set of algorithms and
procedures that implement standard models used in fundamental
astronomy." These include astrometry, calendars, time scales, Earth
rotation and sidereal time, ephemerides (medium precision), geocentric /
geodetic transformations, precession, nutation, polar motion, star space
motion, and star catalogue conversion.

• Jet Propulsion Laboratory Planetary and Lunar Ephemeris software to
duplicate the JPL Fortran programs. They convert files from the ASCII
download format to binary, and cut, splice, read, and test the binary
ephemerides. The files include the same Chebychev coefficients as the
standard JPL binary files and produce the same results (verified by
TESTPO), but the binary format is unique to SofaJpl.

• A bright star subset of the Hipparcos star catalog (re-reduction by
van Leeuwen, 2007) complete to magnitude 3, searchable by star
designation, updated to include the names recognized by the IAU as of
March 2018. The catalog data and designation (name) files are in VOTable
format (a form of XML) and may be modified by the user.

• A collection of classes, mainly built on the SOFA and JPL routines,
which implement common data types and operations in positional
astronomy, such as Julian dates, durations, time scale conversions,
vectors, rotation matrices, decimal to sexagesimal conversion,
calculation of geocentric and topocentric apparent place, etc.

NOTE THAT SOFAJPL IS NOT AN APPLICATION AND IS NOT USEFUL UNLESS YOU CAN
WRITE PROGRAMS. However, I have rudimentary example programs in C++, C#,
and Visual Basic to get the user started. The free Visual Studio Express
(or whatever they call it nowadays) development environment from
Microsoft is a suitable compiler. In fact, SofaJpl was built with VS
Express 2013.

SofaJpl ships as a 313 k .zip file.


The other product I mentioned is Lunar, which is a Windows application,
i.e., requires no programming. To quote the web page:

Lunar4 is a free celestial almanac and navigational sight reduction
program for the Windows desktop environment. Its almanac function
produces barycentric, geocentric, and topocentric coordinates. Its sight
reduction function produces azimuth, altitude, and intercept for the
Marcq St. Hilaire position line method. It also solves for time, given

• altitudes of the Moon and another body, plus their separation angle,
observed from an unknown location (the classic "lunar distance" problem), or
• the altitude of a body observed from a known location, i.e., a
navigational time sight, or
• the separation angle between the Moon and another body observed from a
known location

The available solar system bodies are the Sun, Moon, and planets,
including Pluto. Their positions and velocities are obtained from a Jet
Propulsion Laboratory planetary ephemeris. An internal star catalog (a
subset of the Hipparcos catalog, second reduction) contains all stars
down to third magnitude. There's also a manual entry form for stars not
in the catalog.

The current release is Lunar 4.3, which ships as a 252 k .zip. That
includes the SofaJpl components that it needs. On request I can ship
version 4.4, which has some improvements:

• Remembers some parameters from the last run, such as observer
position, the JPL ephemeris file, and the leap second file.
• Solar eclipse mode, which adjusts the Moon size and position to match
the predictions in the Astronomical Almanac.
• Center of light option for the Moon and planets, instead of the
default center of mass as the basis of the computations.
• JPL Horizons compatibility mode to match the output of the JPL online
facility. (This is accomplished by changing the precession and nutation
model.)

I have not formally released 4.4, but the program is tested and giving
complete satisfaction here. Any changes will be small tweaks to the
appearance. On the down side, the documentation of version 4.4 is pretty
far along but not complete. Also, this is not any sort of mass market
product, even by celestial navigation standards. It was written to
support the things I do, and so in its output you find arcane data such
as the geocentric position and velocity of the topocenter with respect
to the ICRS.

To duplicate all four "equinox" times that I gave in an earlier message,
you need v. 4.4, since 4.3 does not give the geocentric apparent place
of a body with respect to the ITRS (geodetic) coordinate system. It does
take polar motion into account in the computation of azimuth and
altitude, however.

Both SofaJpl and Lunar ship as .zip files which are extracted to any
desired place in your Documents folder. (By default a new folder is
created for the product.) Due to the small size and simplicity of both
products, I don't think an installer is necessary. The problem with an
installer is that it opens a security hole when it's at work, because it
has system administrator privileges. Even with virus protection, there's
an uneasy feeling when installing freeware from "some guy on the net."

Anyone wanting either product should contact me by private email.

   

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