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Author
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Topic: Sight reduction using an external almanac
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David Burch
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posted July 06, 2003 08:05 AM
This is function [6][5][5] in the calculator version, and an option under "Celestial Utilities" in the PC version.
This function puts you into the normal sight reduction routine, but when it comes to computing the almanac data that is usually done automatically, it bounces out of that function and lets you input data from a nautical almanac. The first input is the GHA of the whole hour of the sight (in what ever time system you have chosen) called GHA0, then it asks for the GHA of the next hour up GHA1 ie if your sight time is 13:43:12, then GHA0 is the value at WT=13 and GHA1 is the value at WT=14.
Like wise enter dec0 and dec1, and a few steps later if you are doing sun or moon it will ask you to enter the SD of the body from the almanac you are using, and then it carries on to complete the sight reduction. You do not need to enter d-values or v-values as these can be determined from the inputs and dates you used.
You should get the same as with the internal almanc to within a 1' or so in most cases. You can check to see what values the StarPilot is using with the Precompute function. See topic on Getting almanac data from StarPilot.
From: Starpath, Seattle, WA
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