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Subject: Re: [M]: Choosing Stars for 2-star Altaz Alignment.
From: Bill Arnett
Reply To: mapug@shore.net
Date: Wed Dec 10 00:15:08 1997

At 10:42 PM -0800 12/9/97, James W. Burrows wrote:
>...

Nice work, Jim! This could be very useful. But

> 3813.965 ALDEBARAN ALNILAM

I'm not sure I believe this. If I'm interpreting it correctly this means
that if I use these two stars and am off by 1 minute in centering them that
I will then be off by 60 DEGREES on subsequent GOTOs. I'm sure I've used
Rigel and Betelguese (even closer than these two) on occasion with far
better performance than that.

Nevertheless, the bad end of this isn't very interesting. What's important
is picking the BEST two at any time. It seems to me that given the code
you already have it should be possible given one's lat/long/time/date to
choose the best pair. Heck, there are only about a thousand possibilities;
any computer worthy of the name could find the best pair by brute force
(the job would only get easier by eliminating all those below 30 degrees
elevation).

(Of course, Meade could have done this for us -- power up, enter auto
alignment mode (which requires a known site and more or less right clock),
OTA immediately swings to the first of the best pair and waits for you to
center it, then the second one, done!)

This would make a neat little WWW page with a Javascript component. You
just input your lat/long/time/date and it tells you which stars to pick
(maybe also listing the next best few pairs, too).

(Jim, if you don't want to mess with Javascript, send me your code and I'll
try to translate it to Javascript and do the rest.)

---
Bill Arnett "Science is a way of trying
San Jose, CA USA not to fool yourself." -- Feynman
billa@zNet.com <URL:http://www.seds.org/billa/>