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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robin Stuart
Date: 2024 Mar 21, 07:10 -0700
David I.,
You wrote: Maybe the astronomy community was too focused on blaming their own failings on others...
In the case of the search for Endurance the astronomers of 1914 were well aware of the limitations in their modelling of the motion of the Moon even though it is quoted in the Nautical Almanac to far greater accuracy than it could be calculated. For example in with regard to "Longitude by the Occultation of a Star" C. F. Close in his Textbook of Topographical and Geographical Surveying. https://books.google.com/books?id=IDBRAAAAYAAJ , Close writes
To get full benefit from the accuracy of the method, it is necessary to obtain from some fixed observatory the observed declination and right ascension of the moon during the night in question, so as to correct the co-ordinates given (by prediction) in the ‘Nautical Almanac’; differences even in the second place of decimals of seconds in these quantities appreciably affect the result of the calculation.
On his return to England expedition Physicist Reginald James worked with Greenwich Observatory astronomer A. D. Crommelin to correct the occultation reductions with observational data. One problem is that for occultations the positions of both the Moon and the stars need to be right. The work of James and Crommelin does change the Chronometer Error (CE) by about 20 seconds but ironically the R2 of a linear least-squares fit to observations is actually worse than the uncorrected data. Presumably this is a consquence of additional observational errors being introduced and errors in the catalogued star positions. When modern positions for the both Moon and stars are used, the fit is excellent,
Robin Stuart
