NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Calculators revisited (TI-86, HP 48gx)
From: Bill Murdoch
Date: 2000 Dec 10, 12:43 PM
From: Bill Murdoch
Date: 2000 Dec 10, 12:43 PM
I chose the lower numbered TI-8something calculators to write programs for. They are widely available, cheap, and easily programmed with a Basic-like code. There are lots of used ones around at about half retail price because many high schools require them for algebra and calculus classes, and the kids either dump them at year end or want to move up to a fancier models. I have written two programs both with 200 year +/- 0.1' almanacs. One is a sun sight reduction program and the other is a full featured celestial navigation program. A TI-81 version of the sun sight program was published by Cruising World, and I sold copies of TI-82 programs for both the sun sight and full celestial programs through a classified ad in Ocean Navigator for a few years. The biggest problem with these programs (and the reason that I quit advertising) was that the memory is RAM and can be lost. Even with two separate batteries the programs can be accidentally erased when the batteries go flat. Every month or two someone calls and says their batteries have gone flat and they have lost the program. The sun sight program is short enough that it can be punched back into the calculator in an hour. That is inconvenient, but it is doable. The full celestial program is 28k and takes a week to reprogram through the keyboard. That is not really practical. Either program can be loaded into the calculator from a PC with a TIGraphlink cable in less than a minute, but if you have a PC with you, why is a calculator a particularly good thing? Right now I see the sun sight RAM program being a useful thing, but I have some doubts about a RAM full celestial navigation program. Sun sights will check the GPS, and if necessary, get you where you are going without any hand calculations. Why do you need more? I also think programming a calculator yourself is a good thing. You can learn a lot about calculational astronomy and how the almanac is (actually was) produced. If that interests you it could even be fun. Bill Murdoch
