Next message: Ken Muldrew: "Re: : David Thompson's Navigational Technique"
Jim,
You can find HO 249 online somewhere or another, to peruse it, perhaps
at the Naval Observatory site, http://aa.usno.navy.mil/. As I recall,
it directly gives the altitude and azimuths of various bodies, without
need for much interpolation. So it is very easy to use.
Fred
On Jun 1, 2004, at 6:12 AM, Jim Thompson wrote:
> 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
>
> www.jimthompson.net
> Outgoing mail scanned by Norton Antivirus
> -----------------------------------------
>
>> -----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...
>
