NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: A celestial navigation problem
From: Stan K
Date: 2011 Nov 17, 09:14 -0500
From: Stan K
Date: 2011 Nov 17, 09:14 -0500
A pat on the back for Gary! Nice job throughout, including the intermediate answers, except for one oversight! Now I am confident that my solution is correct and the students should be able to handle it.
The students have the dip correction table, sun altitude correction table, daily pages, etc., provided with the Student Manual. I have provided them all with old Nautical Almanacs for the Increments and Corrections. They have everything they need, but I'm sure they appreciate your concern for them .
The only difference I see between my solution and Gary's is that watch error was overlooked, so the time of LAN should have been 22-07-41.
Also, FYI, the Student Manual uses 23.4º instead of 23.5º at the solstices. (I always say "about twenty-three and a half degrees".)
Thanks for taking the time to look at this.
Stan
The students have the dip correction table, sun altitude correction table, daily pages, etc., provided with the Student Manual. I have provided them all with old Nautical Almanacs for the Increments and Corrections. They have everything they need, but I'm sure they appreciate your concern for them .
The only difference I see between my solution and Gary's is that watch error was overlooked, so the time of LAN should have been 22-07-41.
Also, FYI, the Student Manual uses 23.4º instead of 23.5º at the solstices. (I always say "about twenty-three and a half degrees".)
Thanks for taking the time to look at this.
Stan
-----Original Message-----
From: Gary LaPook <garylapook@pacbell.net>
To: NavList <NavList@fer3.com>
Sent: Thu, Nov 17, 2011 4:20 am
Subject: [NavList] Re: A celestial navigation problem
From: Gary LaPook <garylapook@pacbell.net>
To: NavList <NavList@fer3.com>
Sent: Thu, Nov 17, 2011 4:20 am
Subject: [NavList] Re: A celestial navigation problem
You didn't include the sextant correction table, do you expect the students to figure them in their heads? Dip approx square root of 6, somewhere between 2 and 3 minutes, call it 2.5 (2.4 from table.) Refraction= zero above 63° (to the precision on 1') or 0.2' from table. Or do you use the S.D. of +16.3 minus the 0.2' refraction, total +16.1 or from the sun table of 16.0'. Increment for GHA for time of noon average of the times for both of the 77° 44.1' altitudes, 22:07:46 Z. Do they do the increment in their heads, 15' X 7 minutes plus 46/4' per second = 1° 56.5', same as in increments table. Approx longitude 150° W based on 2200Z time of noon. Sun moves from left to right so must be south. Approx declination 23.5° S, around winter solstice. Approx Ho = 78° so ZD approx 12° so approx lat is 11.5° S. Longitude at noon, 22:07:46 = GHA =149°53.4' plus 1°56.5' so longitude is 151°49.9' W. Hs = 77° 48.7' I.C. + 1.3' Dip - 2.4' S.D. + 16.3' Ref - 0.2' Ho = 78° 03.5' ZD = 89° 60.0' - 78° 03.5' 11° 56.3' Lat 23° 22.6' - 11° 56.3' 11° 26.3' S. So you are on Flint Island. It is easy to memorize the refraction corrections to a precision of 1'; 5' above 10° 4 12 3 16 2 21 1 33 0 63 It's a good test, student must be able to think through the problem. gl --- On Wed, 11/16/11, slk1000@aol.com <slk1000@aol.com> wrote:
|