NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Lunars and the Astra IIIb
From: Eric Haberfellner
Date: 2001 Dec 15, 5:37 PM
From: Eric Haberfellner
Date: 2001 Dec 15, 5:37 PM
I have acquired a copy of Bruce Stark's "Tables for Clearing the Lunar Distance and Finding G.M.T. by Sextant Observation" and am planning to try this ancient and noble art some time in the new year. Is the Astra IIIB a reasonable instrument to attempt this with? In the preface, Mr. Stark mentions that "0.1' of error in the distance causes about twelve seconds of error in Greenwich time". Now, I do not know of a sextant with a guaranteed accuracy of 0.1' (6"). The best that I know of is the Cassens and Plath with a guaranteed accuracy of +/- 9" (0.15'). The Astra IIIb has a stated accuracy of +/- 20" (.33'). Does this mean that it is reasonable to attempt to determine GMT to an accuracy of about 50 seconds with an Astra IIIb? I would also be interested in hearing from others who have tried using Mr. Stark's tables. Eric Haberfellner
