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Just to clarify for the list -- precomputation was reasonably well covered
in our course, and methods are handily available in most computer programs
for CN.  But the specific point that has intrigued me is how much easier it
is to find a star on the horizon before the naked eye can pick it up in the
sky.  That is the trick that was not mentioned or sufficiently emphasized in
our course work.

I had viewed preplanning as useful for beginners and handy for
professionals, but did not realize that it can be essential in order to
improve the odds of shooting a good set of twilight bodies when the horizon
was optimum, early in evening twilight (or later in morning twilight).

As an aside, I spent a lot of time learning to use the 2102-D Star Finder,
but even after working out its mysteries I still find it considerably more
fussy than tapping up the predictions on a handheld or laptop computer.  And
I have not yet learned to use 249.  The best software that I've found for
precomputing a full set of bodies for a given time is the old DOS program
NAVPLANNER by list member Stanley L. Klein: it generates great lists of
bodies sorted by magnitude, highlighted by alitude window.  It also provides
sunrise/sunset data for the date/DR position:
http://jimthompson.net/boating/CelestialNav/NavsetPC.zip
Hopefully Stanley can find time to do up a Windows version (wink, wink).

Jim Thompson
jim2@jimthompson.net
www.jimthompson.net
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> -----Original Message-----
> From: Henry C. Halboth
> You bring up a very good point - pre-computation of altitude and azimuth
> seems to be a neglected wrinkle in practical navigation and is barely
> mentioned in most navigational texts to which I have quickly referred...

   

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