NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Latitude by Lunar Distance
From: Peter Fogg
Date: 2006 Oct 7, 17:00 +1000
From: Peter Fogg
Date: 2006 Oct 7, 17:00 +1000
On 10/5/06, Frank wrote:
>
> I am somewhere southeast of New England, rough DR = 38N, 70W, early in
> the morning of October 11, 2006. It's the middle of the night and a bit
> hazy, too. The sea horizon is invisible. But I can see the Moon and
> some bright stars... At 06:36:00 GMT I look up high in the South at the
> Moon with Aldebaran below it. With my sextant, I carefully measure the
> angular distance (Far limb) between the Moon and Aldebaran and find
> that it is 11d 39.9'. Then I turn to Pollux and measure the distance
> from that star to the Moon (Near limb this time). I find that the
> Pollux-Moon lunar distance is 38d 13.1'. The GMT for this sight is
> 06:39:00 exactly.
Here are the calculated OBSERVED altitudes and azimuths of the
stars and the Moon. The distances between the bodies has then been calculated.
At Lat N38d, Lon W70d, on 11 Oct 2006 (at sea):
GMT Body Azimuth Altitude
6h 36m Aldebaran 134.62d 62.06d
Moon(Centre) 110.68 67.34
Distance between bodies 11.41d
6h 39m Pollux 79.04d 34.18d
Moon(Centre) 111.62 67.88
Distance between bodies 38.47d
(Frank's distances were 11d 39.9m and 38d 13.1m)
At Lat N41d, Lon W74d, on 11 Oct 2006 (approx New York):
GMT Body Azimuth Altitude
6h 36m Aldebaran 132.17d 57.76d
Moon(Centre) 111.85 63.32
Distance between bodies 11.37d
6h 39m Pollux 78.78d 31.72d
Moon(Centre) 112.73 63.83
Distance between bodies 38.46d
At the same time in New York, 3 degrees to the north and 4 degrees to
the west, almost exactly the same angular distances. As would be
expected. The small differences are thought to be due to parallax and
refraction, not the change in position. How can position be determined
from these observations?
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