NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Equal altitudes problem of March 9
From: Mal Misuraca
Date: 1997 Mar 10, 14:47 EST
From: Mal Misuraca
Date: 1997 Mar 10, 14:47 EST
The time of the last sextant observation in the column from the problem
posted yesterday is in error. The last time should be "22:09:05," instead of
"21:09:05."
The nautical almanac data for observations of the sun on August 3, 1995 is as
follows. If you need GHA and dec for other exact times, you can either get it
from the proper nautical almanac, from Celesticomp V or another computer
source, or from the Interactive Computer Ephemeris ("ICE"). ICE was used to
generate the following figures, and I will be happy to look up others and post
them within a day or two of being asked.
Time GHA Dec
21:09:05 135.438 17.271 N
21:19:05 138.138 17.270 N
21:25:00 139.434 17.270 N
21:27:00 140.125 17.269 N
21:30:30 141.050 17.269 N
21:35:14 142.161 17.268 N
21:39:00 143.126 17.268 N
21:39:05 143.142 17.268 N
21:39:10 143.151 17.268 N
21:42:56 144.151 17.267 N
21:47:40 145.176 17.267 N
21:51:10 146.151 17.267 N
21:53:10 146.451 17.266 N
21:59:05 148.138 17.266 N
22:09:05 150.438 17.265 N
These times do not coincide in all cases with the problem you were given, in
order not to make the problem too obvious in light of the almanac data.
Nonetheless, if you cannot work the problem without other times' data, I will
oblige.
Thanks to the Net for the opportunity to explore this old system, which has
now got a renewed and special appeal---for being very simple to teach, now
that GPS makes many small vessel sailors impatient about learning celestial.
This means equal altitudes may become, at least for my students, the salvation
of a passage turned nightmare when a GPS failed, or simply a source of extra
peace of mind and satisfaction, to know as Chichester said that celestial is
good if only because "it is the one form of navigation not in the control of
any government."
I hope you will summon me for more information, if you feel you need it.
Maybe you do, and maybe you don't. (Hmmm.)
Mal Misuraca
