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Author
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Topic: Nautical Almanac, Four Year Cycle
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SMadden
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posted February 12, 2006 10:02 AM
I've read that a Nautical Almanac that is exactly four years out of
date can be used as a back up source of data for Celestial Navigation.
Why is this? Is there a source of four consecutive years worth of old
Nautical Almanacs in case one might want to explore or purchase them?
From: Greeley
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David Burch
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posted February 12, 2006 12:26 PM
What you have read is essentially true for sun and star data. It is not valid for moon or planets.
the main corrrection for these bodies is the leap year correction to days per year, and thus, 2003 sun and star data would be about the same as 1999, and 2007, etc. The results are not exact (else why have an annual publication) but they are certainly good enough for a backup sight reduction.
But you do not need 4 almanacs to take advantage of that fact. In each almanac in the back text sections, they explain how to use the almanac for other years.
From: Starpath, Seattle, WA
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