|
|
Subject: Re: Calculators
From: Tony (anthonys@XXX.XXX)
Date: Mon Sep 06 1999 - 23:07:07 EDT
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
|