NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Were Short methods really Short?
From: Stan K
Date: 2016 Aug 7, 19:12 -0400
From: Stan K
Date: 2016 Aug 7, 19:12 -0400
David,
I've been out of touch for the last few days. I just got back and saw your message. Without working through the numbers, which I will probably do later today, a few things come to mind:
The app that give the sun's azimuth at sunrise probably gives the azimuth when the upper limb is on the visible horizon. Bowditch Table 27 give the azimuth of the sun when its center is on the celestial horizon. (Table 28 is used to correct this to the visible horizon.)
I suspect that these considerations might account for the discrepancies.
Stan
-----Original Message-----
From: David C <NoReply_DavidC@fer3.com>
To: slk1000 <slk1000@aol.com>
Sent: Fri, Aug 5, 2016 10:24 pm
Subject: [NavList] Re: Were Short methods really Short?
From: David C <NoReply_DavidC@fer3.com>
To: slk1000 <slk1000@aol.com>
Sent: Fri, Aug 5, 2016 10:24 pm
Subject: [NavList] Re: Were Short methods really Short?
The work sheet for Ageton Classic has entries for Prime Vertical calculations. The second of the calculations uses the formula for amplitude at rising
sin A = sin d * sec L.
sin A = sin d * sec L.
The worksheet (incorrectly I believe) describes the result as Z.
On 17 July 2016 when L = S41° 06.5' and d = N21° 08.6' Ageton Classic gives Z=28° 36'. An app gives the sun's azimuth at rising as 62.3° or 62° 18'.
28° 36' + 62° 18' = approx 90°. Why the result is not exactly 90° is probably a thread in itself (unless I have made an error in my calclations).
As a check, for Lat 41° and Dec 21° Table 27 in Bowditch gives amplitude = 28.3° or 28° 18'.
