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Subject: Re: [M]: LX200: Prob{good pair}?
From: Bill Arnett
Reply To: mapug@shore.net
Date: Mon Oct 21 02:34:08 1996

At 10:28 PM -0700 10/20/96, James W. Burrows wrote:
>...
>Computer exercise: find for your location if there's ever a time without
>a good pair, using the positions of the real alignment stars.

This was a fun exercise. I made a quicktime movie (4.5 megabytes!) of the
sky rotating for 24 hours with the zenith at the center and the whole
horizon showing using Starry Night on my Mac. I had only the alignment
stars labeled so they are really easy to find. I then cut out a paper mask
so that I could see just the region between 30 and 60 degrees elevation and
stepped thru the movie.

The answer: yes, from San Jose (lat 37N) there are a few times when there
are no alignment stars between 30 and 60 degrees altitude and at least 90
degrees apart if you don't count Polaris (the manual specifically states
not to use Polaris since "RA changes fast at the pole"). But in no case
did the situation persist for long. And if you relax the altitude rule
just a little then there's no trouble.

Of course, this assumes a perfect horizon. In real life there may be many
more times when there are no good alignment stars. I guess one just has to
make do as best he can and then realign when the situation improves :-(

---
Bill Arnett              billa@znet.com           http://www.seds.org/billa/

  "I know that I am mortal and the creature of a day; but when I search
   out the massed wheeling circles of the stars, my feet no longer touch
   the earth, but, side by side with Zeus himself, I take my fill of
   ambrosia, the food of the gods." -- Claudius Ptolemaeus (Ptolemy)