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Topic: Page 11-61, bottom Choosing a-Lon
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David Burch
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posted July 24, 2008 02:43 PM
The rule for figuring out the degrees part of the a-lon is missing a phrase. Compare to the paragraph following. The first case is for GHA minutes less than 30 and the second paragraph is for GHA minutes greater than 30.
Here is a way to write the Rule given there:
Here is the procedure, given DR-lon° and DR-Lon' as well as GHA° and GHA'.
For example if DR-Lon = 122° 45.6' then DR-Lon° = 122 and DR-Lon' = 45.6
Step 1. Choose a-Lon° = DR-Lon° and choose a-Lon' = GHA'
Step 2. Now look at the difference between DR-Lon and a-Lon. Call this Delta
Step 3. If Delta is less than or equal to 30' you are done. The AP = a-Lon° a-Lon' = DR-Lon° GHA'
Step 4. If Delta is greater than 30', then we need to change a-Lon° by 1°, either up or down according to Step 5.
Step 5. If GHA' is greater than 30, then decrease a-Lon° by 1°, but if GHA' is less than 30, increase a-Lon° by 1°.
From: Starpath, Seattle, WA
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