NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Faint stars easier to find on the horizon first?
From: Fred Hebard
Date: 2004 Jun 1, 08:26 -0400
From: Fred Hebard
Date: 2004 Jun 1, 08:26 -0400
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 > jim2@jimthompson.net > 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... >