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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Ulugh Beg's sextant
From: Frank Reed CT
Date: 2006 Mar 26, 18:05 EST
From: Frank Reed CT
Date: 2006 Mar 26, 18:05 EST
Herbert, you wrote: "E. B. Knobel investigated the accuracy of Ulugh Beg's star catalogue in the introduction to his edition of it. After grouping the stars into northern, zodiacal and southern ones, he shows a systematic bias in longitude of 18', 14' and 4' respectively. Then he subdivides each group into 18 sub-groups, each 20 deg of longitude wide. The corresponding errors in longitude fluctuate about a quarter of a degree around those means, occasionally a little more. Therefore, some longitudes are more than half a degree off the truth. The errors in latitude are of a similar magnitude. From what I see, they may be just marginally better than those of Ptolemy/Hipparchus." Very interesting. Thanks. It strikes me that the accuracy in latitude should be better than that in longitude. No? What is the origin of this myth that the positions were accurate to a few seconds of arc? A number of web sites quote an article by "Kevin Krisciunas" on this point. Maybe it's just that single source. -FER 42.0N 87.7W, or 41.4N 72.1W. www.HistoricalAtlas.com/lunars
