is there any online documentation for the HP41 ASTRO*ROM package from Elgin, Knowles & Senne?

I recently acquired one to entertain my navigation math hobby.  I am not a surveyor and would not use the application for any practical purpose.  

I am intrigued to learn more about old school surveying techniques and look forward to lurking on the forum. 

Best Regards

Todd Deckard

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Greetings Todd;

Have you tried contacting Elgin, Knowles, and Senne Inc. in Rolla, MO? I checked their 'Previous Software Products'  tab at their web site and was not able to find a link to their early software manuals. In fact the older software is no longer in production. Perhaps they would be willing to provide some documentation. Here a link to their company in Rolla.

Also the US Dept. of Interior BLM used to produce several Astronomical Observation Training Manuals and Ephemerides back in the day. It's possible some of that documentation would be available as public information.

Bernie Marocco

Greetings Bernie,

Excellent suggestion. I did reach out to them via the website earlier and just now received a response from Dr. Elgin offering to send me a copy by post!  I will ask him if I may digitize it to share it electronically.   

There is also a 2008 Ephemeris manual online that does sort of get me started.  

I will let you know when I receive the module documentation. 

My understanding is that the algorithm presumes you have a very accurate latitude and longitude and are trying to calculate a precise azimuth from that point based on a solar or polaris observation.  Its "sideways" from the classic navigation question of computing a latitude from an altitude. 



Hi Todd;

Here's an archive link giving a synopsis and technical notes to one of BLM's Training manuals 'Selected Computations of Astronomical Observations'  circa 1971. The document is archived at the BLM Library at the Denver Federal Center:

At the top of the page you will find a link to the full text. It served as an excellent reference for solar and celestial observations.

Best regards;

Bernie Marocco

diving into "Selected Observations ..."  I had not seen that one.   Thanks!

Hi Todd,

You can join hp to see anything HP 41. Warren Furlow runs it,tons of info on the HP41.

There have been several discussion here,  on Sun and Star shots,mine I discuss using a Hp 41 CX and programming for it. I also started a HP 41 Group here at this site. I do not have a Astro*ROM *MOD

but the site has info on it and downloads.

You will also find NAV PAC's and programs, go over the complete library 

Bernie and I are good friends.


Excellent link.  I am very familiar with Warren's database.  If you check out my HP41 ROM SLANTR, its a collection of routines to update an airman's ded reckoning position and refine it with radio fixes.  Perhaps not relevant to landsurveyors, excepting that surveying is a form of *very* precise navigation. 



I don't know anything about the ASTRO ROM but the old HP 41 had a program to calculate azmuths from star shots & sun shots. GPS has added another dimension & made the associated calculations & corrections more complicated but not much else has changed since Christopher Columbus sailed to the new world. The biggest advantage of using satellites over stars is you also get a distance from the satellites as well as an azimuth. That equates to a much more accurate position much quicker. The newer calculators such as the HP 50 or 49 G will do the math. You may have to find the formulas but they should be pretty easy to find on the net. They are also programmable. You might want to look at some of the courses designed to prepare surveyors for the PLS or "SURVEYOR IN TRAINING" exam.


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