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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Instrumental errors
From: Fred Hebard
Date: 2015 Jun 26, 21:58 -0400
From: Fred Hebard
Date: 2015 Jun 26, 21:58 -0400
Regarding the Index Error, Chauvenet, in “A Manual of Spherical and Practical Astronomy, Vol 2,” presents on page 98 as methods for checking index error the star coincidence method and the apparent diameter of the sun (https://books.google.com/books?id=FVdRAAAAYAAJ&printsec=frontcover&dq=editions:QmrAl-CNghIC&hl=en&sa=X&ei=GAGOVb-IOMm5ggS0gamQBQ&ved=0CDMQ6AEwBA#v=onepage&q&f=false). (Note that the first few hits of Volume 2 on Google Books are actually scans of Volume 1). Chauvenet makes no mention of measuring coincidence of the two sun images. He does mention using a horizontal orientation of the instrument when oblateness might be an issue and mentions using coincidence of the horizon when discussing star coincidences, but states that coincidence of the horizon is an inferior method.
Chauvenet probably represents the apogee of scholarly treatment of the sextant.
Fred
