A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: John D. Howard
Date: 2019 Dec 22, 12:11 -0800
First of all, let me say that the method in Mary Blowitt's is valid. I was giving my personal dislike for the method, not that is was incorect. It seemed you were asking about errors derived from the wrong scale ( 53 D vs. 53 D 30 M ). I tried to show that the only error would be in the longitude readout, 0.2 minutes of arc.
Vol. one of AP3270 ( like the HO 249 ) gives data for stars for a valid year, say 2015, and then has tables to tweek the data untill the next vol.is published, 2020. I do not use the tables for sight reduction, instead use calculators. Not untill David Pike's post did I know why anyone would like Mary Blewitt's method.
Why you got a different cosine value I cannot discover. I tried sine, tangent, log, and nothing gave me -0.918282. ( For what it is worth, every computer using Windows has a built-in calculator that will pop onto the screen. ) The only thing I can think of is you mis-typed. ( I typed 35 D instead of 53.5 D )