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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2015 Nov 22, 12:07 -0800
Gord,
When using Pub 249 vol. 1 (selected stars) the look up is local hour angle (LHA) Aries. When using Pub 249 vol. 2,3, or Pub 229 the look up is the local hour angle of the body which is in your case for Vega GHA + SHA +/- Lon. = LHA Vega. Using 249 saves lots of math by using LHA of Aries and doing the SHA work up for seven selected stars. This is what makes the table quick for sight reduction and quick for precalculating stars for the twilight period. You will be using a different assumed longitude for Pub 249 vol. 1 to get a whole value LHA of Aries vs. reducing an individual body by Pub 249 vol 2 &3 or Pub 229. Using your Vega values at my location I needed to use an assumed longitude of 119° 32' W for 249 (selected stars) to get LHA Aries of 162°. For 229, 249 vol. 2&3 I needed to use an assumed longitude of 119° 10' W to get LHA Vega of 243°. A case of apples and oranges as the saying goes.
Greg Rudzinski
From: Gord Cudlipp
Date: 2015 Nov 21, 23:10 -0800On at 14 h, 48 min, 56 s, (UCT) on Nov 20th, I reduced a sight for Vega using HO 229 Marine Sight Reduction Tables Vol 4. Everthing work out fine, my LHA was 239 degrees and corrected Hc was 12 degs 05.4 min (which was vey close to my Ho). However, when I used HO 249 Vol 1 (Selected Stars) it did not work at all. I entered the table for LAT 49 degrees North with an LHA of 239 and got an Hc 59 degs 36 min. I can't figure out what I'm doing wrong!
