NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Lars Bergman
Date: 2013 Jan 14, 00:58 -0800
Kermit wrote
"2 - Strange Azimuth computation error from the Navigator for SIRIUS, one of the only 2 bodies used for Longitude determination. Current determination is 123d4 while the Navigator computed 106d38'7 "
Well, 106d38'7 is not the azimuth at all, but the body's polar distance, i.e. 90d minus declination, which is used in the hour angle calculation. As declination is opposite name to latitude polar dist becomes larger than 90d.
One thing that I haven't been able to understand is the computation for Greenwich hour angle. For Sirius there is a sum, below GMT 18h17m27s,
51 49.4
275 00.0
6.8
--------
326 56.2
giving GHA Sirius. 6'8 seems to be a correction for 27s, but the other two quantities? In modern notation it should be GHA Aries and SHA Sirius but looking into an on-line NA, I get GHA Aries for 18h17m to 67d33'2 and SHA to 259d16'3. Together with the 27s correction for GHA Aries of 6'8 this sums up to 326d56'3 for GHA Sirius, only 0'1 off. Can anyone explain those numbers?
Lars, 59N 18E
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