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My Windows program to solve lunar distance navigation problems has
finally been updated to eliminate the bug that prevented it from working
under Windows 8. This was possible thanks to a rewrite of the supporting
SofaJpl "astronomy engine" DLL. All the Fortran routines in SofaJpl have
been replaced with C++ or C#, thereby fixing the Win 8 bug and
eliminating some annoyances and limitations in the handling of JPL
planetary ephemerides.

This new release has not yet been subjected to all the tests listed at
the Web site. But the two main tests — the Sun and Pollux lunars — are
very good. I don't expect any problems with accuracy. To the contrary,
the former version had a flaw (now corrected) in the deflection of the
vertical computation.

In addition to solving the classic lunar distance problem (one
separation angle and two altitudes), the program can also

• Determine time from lunar distance only, observed from a known location.

• Determine time from a single altitude at a known location (a time sight).

• Solve for position line azimuth and intercept.

• Generate geocentric apparent position data, as in the Nautical
Almanac, but with higher accuracy.

• Calculate eclipse and occultation data. The program isn't optimum for
this application — you must find the contact times by trial and error —
but the results are accurate. A few years ago I used the previous
version to analyze a near occultation observed from Alexandria in the
3rd century BC. Recently I recomputed the event with more appropriate
software and found the differences insignificant.

Available bodies are the Sun, Moon, all planets (including Pluto) and
all stars to magnitude 3.0. Data for any star not in the built-in
catalog may be entered by hand.

I would appreciate any feedback regarding success or failure in getting
the program to run. Include your Windows version. One user with ver. 7
reports his antivirus software blocks the lunar program for an unknown
reason.

Speaking of security, installation is improved from the previous
version. The "installer" is just a .zip file, which you extract into the
desired directory. Thus the software will install into a Windows limited
account. You don't need system manager privileges, and for security I
don't recommend installation via a system manager account.

http://home.earthlink.net/~s543t-24dst/lunar3/index.html

   

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