Elgin, Knowles & Senne, Inc.

310 E. 6th St.
Rolla, MO 65401










History of ASTRO*ROM


Concurrent with the development of the Lietz Ephemeris, Joe Senne had been developing algorithms for planet and star coordinates and celestial objects rise-set tables. Since the HP 41 Calculator was designed to accept Read-Only-Memory (ROM) modules. It was decided to develop an astro-azimuth program that would fit in a 4K module. This module was to contain internal ephemeris generation to calculate and average multiple azimuth observations. Also the ephemeris should be accurate to less than 2 arc-seconds, good for up to year 2010 and calculate six observations in about two minutes.

However even using the HP 41CX calculator there was not enough programming memory available, so the program had to be broken into two main subroutines. Each subroutine was written separately plus a small dummy subroutine for checking. When completed the program could calculate azimuths for solar, Polaris and other stars. Time was taken from the internal clock in the calculator and automatic horizontal angle input was available when using a Lietz total station. In addition an altitude-azimuth program (SUNH) for a solar track across the sky was also included.

By late 1985 the program was ready to be burned to a module. We contacted Firmware Specialists, Inc., a consulting firm connected with Hewlett-Packard, and David Conklin worked with us to get the ASTRO*ROM modules burned. 1000 modules were made and a small user manual printed. These sold out by 1989, which gave the opportunity to revise ASTRO*ROM. We discarded the SUNH program to free memory for storing field observation data, improving the setting of the internal clock, inputting stopwatch times, and storing star coordinates. The new module was called ASTRO*ROM2. This time only 500 modules were burned because HP was coming out with the new HP 48 and we could see the demise of the HP 41. The HP 48 used a programmable card instead of a module and a different programming language than the HP-41.

By 1991 the astro program had been revised for the HP 48 and enlarged to store 63 star positions. It was much faster than the HP-41 and would calculate six observations in 28 seconds. We purchased a card burner and could burn our own 32K OTP (One Time Programmable) and later 128K flash cards.

In addition to astro and state plane programs for the PC we also made a state plane coordinate (SPC83) card for the HP 48. This card, for the 1983 datum, containing all state constants, would convert geographical to state plane coordinates and the inverse. It would also convert from ground to grid distance and Geodetic to grid azimuth and the inverse.








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