A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Paul Bedel
Date: 2019 Jan 8, 12:21 -0800
I wonder about this extract of the Alain Gerbault's logbook on march 30th 1925. He indicates some details of a calculation of a fix by pole star (latitude) and Betelgeuse (hour angle and longitude). Latitude by pole star is 10° 09' N but he uses 10° 08' N (?); altitude of Betelgeuse is 17° 57'. The calculation of hour angle is quite correct, with Lat = 10° 08' N, Dec = 7° 23' N and Alt = 17° 57'. But, it remains three questions:
1) What is the meaning of arcs 49° 56', 47° 41' and 15° 25' ?
2) Idem for the logs 10,2658 and 0.7172 knowing that 9.5486 is the log of haversine HA ?
3) Gerbault mentions Johnson's tables (cloudy weather ?) but nothing lifelike in A. C. Johnson's books; is it the same Johnson?
Thank you in advance for your interesting contributions ... and a very happy new year.
PS: A. Gerbault was sailing alone around the world in 1923-1929 on is cutter "Firecrest"; I have found the page of his logbook in "Alain Gerbault, vie et voyage d'un dandy révolté des années folles" by E. Vibard (1989).