NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Calculators
From: Tony S
Date: 1999 Sep 06, 9:07 PM
From: Tony S
Date: 1999 Sep 06, 9:07 PM
Bill: Many thanks for your expansive reply. I can agree with you thoroughly as I have "walked the walk" through many stages since about 1976. Most of my early stuff was done with various HP calculators; then I reached "heaven" with the HP 67. This later led to the 41C/CV and TI 99/4A; then the dos & win computers. The learning experiences have been been most rewarding. Sure wish we would hear from Ben Smith about progress on his "yacht". Tony Bill Murdoch wrote: > > I guess my first point is that astro navigation calculators run from $10 trig > function calculators to Pentium IIIs. All of them are useful. The first $10 > replaces several pounds of sight reduction books by solving the cosine > formula. The next $25 will get you a solar almanac and replace the dip and > refraction tables along with the pencil needed to do the sums to reduce a sun > sight. The next $50 will buy enough calculator to replace all the other > information in the Nautical Almanac. The last $2000 makes it all very slick. > There are good reasons for stopping anywhere along that path; especially in > the days of GPS when astro is basically a hobby. > > My second point is that programming a calculator (or computer) is for some > people fun. Sure, it is easier to buy a Celesticomp, Palm Pilot or PC, load > in a program, and go to it. But, there is a sense of accomplishment in > doing it yourself. The easiest path may not be the most rewarding - it is > easier, cheaper, and faster to fly from Charlotte to Marsh Harbor than to > sail down from Beaufort, but some prefer to sail. > > My third point is that life is about learning. Learning how to take a sight. > Learning how to reduce it. Learning how to clean and care for a sextant. > And, learning how all those numbers in the almanac are calculated. Almost > every JN student asks where the numbers in the almanac come from. Programing > your own astro calculator can be a path to that answer. > > I agree with you, the sun is easy. After making the conversion of years, > months, days, hours, minuets, and seconds into a single measure of time, > after handling the data sight data input and the output, and keeping an > accuracy of 0.1', about this much program memory is needed to calculate > almanac data in a TI calculator: > Aries - 75 bytes > Sun - Aries plus 700 bytes > Moon - Aries plus 2000 bytes > Planets - Aries plus Sun plus 600 bytes plus for > Venus - 600 bytes > Mars - 1000 bytes > Jupiter - 1500 bytes > Saturn - 2000 bytes > 92 stars - Aries plus 2500 bytes > But, the sun is also the most useful body. You may need no more. (It is a > shame the moon's motion is so complicated. It woudl be a good second body.) > > Bill Murdoch