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Re: Interpolation to latitude
From: Ark Shvetsky
Date: 2009 Nov 8, 23:22 -0800
From: Ark Shvetsky
Date: 2009 Nov 8, 23:22 -0800
L.Gray, "100 Problemsin Celestial Navigation" Problem 1-1
"...sailiing from New York to Azores... May 13, 1993. DR position at 0730
(GMT) will be 40 deg 10' N and 50 deg 15' W. Planning for a round of
twilight sghts..."
50 deg 15 ' of long is equal to 3 hr. 21 m, which we add to LMT to get GMT.
LMT GMT
Nautical twilight 0337 0658
Civil twilight 0414 0735
Sunrise 0446 0807..."
Appendix B (which is "how to")
"1. On the right-hand daily page of the almanach, enter the upper half of the
table (a.m) with the expeced DR latitude at the time of the twilight.
(interpolate for latitude, either by eye or mathematically)..... Convert each
LMT to GMT by adding... or subtracting .. the time equivalent of the
expected DR longitude-found on the first yellow page in the back of the
almanach"
My question is: why there is no mentioning of interpolaion for the longitude
in calculating twilight phenomenon? As I mentioned before, I think the
interpolation for the zone meridian ( in this case 45 deg W) should be
included in calculation also. I don't think it was included.
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