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Re: Refraction, Cassini model
From: Paul Hirose
Date: 2018 Nov 28, 15:33 -0800
From: Paul Hirose
Date: 2018 Nov 28, 15:33 -0800
On 2018-11-27 18:45, Roger W. Sinnott wrote: > By the way, the latest (3rd ed., 2013) of the Explanatory Supplement to the Astronomical Almanac, on pages 277-280, gives a number of methods for finding the atmospheric refraction. Along with several low-accuracy formulas, it describes a precise algorithm for calculating refraction using numerical integration. This method is written out in clear steps, like the outline of a computer program. That last sounds like the algorithm in the 1992 Explanatory Supplement. Andrew Young (not Bruce Young as I originally wrote — thank you for the correction) criticizes its refractive index formulas: "Unfortunately, this incorrect and obsolete formula was also used by Hohenkerk & Sinclair (1985), from which it was copied in the new (1992) edition of the Explanatory Supplement (see the middle of p. 142 for the obsolete formula there); so we can expect to continue to see it crop up again in the future." https://aty.sdsu.edu/explain/atmos_refr/air_refr.html The 1985 Hohenkerk and Sinclair work was Nautical Almanac Technical Note 63, "The computation of angular atmospheric refraction at large zenith angles." http://astro.ukho.gov.uk/nao/technotes/ Young notes some issues with that document: https://aty.sdsu.edu/bibliog/bibliog.html#Hohenkerk+Sinclair1985q In the Technical Note I discovered some trivia about the Nautical Almanac: the low altitude refraction table was computed with the 1944 model of Garfinkel: http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1944AJ.....50..169G&db_key=AST&page_ind=0&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES
