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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Astronomical Refraction: Computational Method for All Zenith Angles
From: Frank Reed CT
Date: 2005 Aug 17, 00:17 EDT
From: Frank Reed CT
Date: 2005 Aug 17, 00:17 EDT
Marcel asked: "Does anyone of you know where to obtain a newer program in source code and with a description of what it does?" No source code, but there's an excellent short article by Auer and Standish on this topic including sample calculations for various temperatures and pressures and even for negative altitudes as seen from 15,000 meters observer height (just the thing that got you started on this!) in the Astronomical Journal for May, 2000 [AJ,119:2472-2474,2000 May]. This is the calculational approach recommended in the 'Explanatory Supplement to the Astronomical Almanac', so it doesn't get much better. Checking against the tables in the Nautical Almanac, the refraction values generated by this algorithm are an exact match except for differences of a couple of tenths of a minute of arc very close to the horizon. You can get the article in .pdf format from ADS here: http://adsabs.harvard.edu/advanced_fulltext_service.html . But to save searching and for those list members who want the article but don't get along well with pdf files, I've made a link to .gif copies of the article's three pages here: http://www.HistoricalAtlas.com/lunars/ref.html . -FER 42.0N 87.7W, or 41.4N 72.1W. www.HistoricalAtlas.com/lunars
