A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David C
Date: 2016 Aug 5, 19:12 -0700
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.
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'.