# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Calculators for Navigation**

**From:**Bill Murdoch

**Date:**1999 Mar 13, 7:01 PM

In a message dated 3/12/99 7:47:41 AM EST, titom{at}ix.netcom.com writes: > What type of calculator is the best for working the calculations, should it > be programable? After you master the needed calculations and plotting by hand, Nautical Almanac, and sight reduction tables; I think you would be best off with a programmable calculator. Calculators are (still) cheaper than computers and are much more rugged. Much of my enjoyment of celestial navigation has come from programming programmable calculators for sight reduction. I started off with a HP-11C that had enough memory to hold the cosine sight reduction formulas and the other calculations that are detailed in the appendix of the Nautical Almanac. That worked well enough, but I wanted to free myself from looking up the astronomical data in the almanac. I wanted to calculate the data myself. From the British Library I got a copy of the booklet, B. Emerson, N.A.O. Technical Note Number 47 - Approximate Solar Coordinates. The booklet had reasonably short 0.1' formulas for the GHA, declination, and semi diameter of the sun that are good for a couple of hundred years. I used them to write a program for a TI-Galaxy 67 calculator that would produce an intercept and azimuth given the day, date and time, the D.R. latitude and longitude, the solar limb observed, the sextant altitude, the index correction, the height of eye, the temperature and the pressure. I worked the program into a January 1994 article for Practical Boat Owner, "A Sun Sight Calculator for �17". A year of two later I modified the program to run on a TI-81 calculator. That program was published in Cruising World in March 1996. I later rewrote it to run on a TI-82 or TI-83. The TI-82 had enough memory to do much more, so I expanded the program. In that calculator program I included the moon, four planets and 92 stars. I added the ability to reduce multiple sights to a lat/long fix, mercator sailing, great circle sailing, sunrise - sunset prediction, and a bunch of other things. I was unable to find a publisher for the program (It is about 200 pages typed.) and sold it for three years through a classified ad in Ocean Navigator. All of this has been great fun. I have learned a lot, met quite a few interesting people, and filled more than a few quiet evenings. Bill Murdoch =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-=-= TO UNSUBSCRIBE, send this message to majordomo{at}roninhouse.com: =-=-= unsubscribe navigation =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-