A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Antoine Couëtte
Date: 2018 Apr 28, 23:34 -0700
Excellent Module !
When it was published - in early1980 - this HP41C [Marine] NAVIGATION PAC Module was ahead of everything else comparable (i.e. hand-held calculator Marine Nav Module) in particular because it was "alpha numerical" and also because because it pioneered the first internal / self contained Ephemeris Computation Software reasonably accurate for CelNav over the 1900-2100 time-frame.
This HP41 NAV Module makes an extensive use of the then extremely celebrated enclosed paper Low Precision Formulae for Planetary Positions by Thomas C. van Flandern and Kenneth F. Pulkinnen. While its Introduction last sentence states that "The full precision formulae (1" or better) with unlimited time validity are being developed." to the best of my knowledge such 1" accuracy formulae were never published.
The Stars Almanac of this module is based on the stars position for year 1979 (or so) and while it includes at least Precession effects for any future or past epoch, I do not think that it takes the Stars proper motions in account.
Anyway, this highly praised and celebrated module certainly was the most avant garde Nav Module for its time of release.
Which version do you have ?
You can see it through excecuting CATALOG 2 (or a number different from 2 depending of your actual HP41 Handheld Calculator version).
If you have Rev 1A, you need a smal "patch" for Acrux Declination which is incorrect in Rev 1A. If so, I included such "March 1981 HP-41 Navigation Pac Addenddum Card " so that you can manually insert it into RAM. The correct Acrux declination for this module should show as -62.9275 . To the best of myknowledge, any version starting from REV 1B included has been considered as bug free.
Do you have the User's Manual ?
If not, check onto http://www.hpmuseum.org/ and you should be able to get a scanned copy of it, or post a message onto http://www.hpmuseum.org/forum/ , which by the way is an extraordinary and amazing forum extremely elaborate on a technical standpoint.
Good Luck, and do not hesitate to get back to me if need additionnal help
Antoine M. "Kermit" Couëtte