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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Bowditch Long Term Almanac Tables
From: Dan Allen
Date: 2002 Oct 23, 09:39 -0700
From: Dan Allen
Date: 2002 Oct 23, 09:39 -0700
One of the nice features of the Bowditch volumes from 1958 until 1984 is Appendix H: Long Term Almanac It made carrying along a Bowditch (or two from 1975 until 1984) self-contained: it had the theory and the tables needed to do "lifeboat" navigation. Now of course this useful table has been removed with no replacement in later editions. How sad. (These editions also had H.O. 211 as Table 35, "The Ageton Method", also now deleted.) The Appendix had two pages for the Sun's GHA and Dec for 10 different dates per month, for each month of the year. There are corrections based upon year so that the maximum error for altitude would not exceed 2.0' of arc. It also has information for 38 navigational stars in a compact little table with promised errors of less than 1.3' of arc, as well as a table of the GHA of Aries, along with 2 auxiliary tables. The whole thing with explanation takes up about 5 pages. Very neat. Question: does anyone know the source of this table? Is it just Newcomb's formulas put into a table? (Newcomb's formulas were the basis of the Nautical Almanac before computers and DE405.) Question #2: could we come up with a newer, better, more compact long term almanac ourselves? Just a thought. Dan