NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Andrés Ruiz
Date: 2007 Oct 2, 09:38 +0200
In the book: “An Introduction to Practical Astronomy“, (Elias Loomis, NY, 1860)
Chapter VI contains an old method of determining the latitude of a place by observations of a circumpolar star at the time of its upper and lower culminations
· It is independent of the declination of the observed star
· It is as free as possible from the errors of refraction
If both altitudes being measured from the north horizon:
Latitude: B = 1/2*(H_up + H_low)
Where H is the altitude measured by the sextant, corrected for index error, dip and refraction.
This past weekend I try to use the method, and I have not been able to find a star that had the two transits at the same night.
Simulating some data, the problem from my latitude at this moment is the difference between the times of the two phenomena: one by day and another at night.
UT H
h m Culmination º ´
29-sep-2007 Polaris 2 20 Upper N 44 1.2
29-sep-2007 Polaris 14 18 Lower 42 36.8
29-sep-2007 Merak 10 39.1 Upper N 76 59
29-sep-2007 Merak 22 37.1 Lower 9 39.8
29-sep-2007 Alkaid 13 24.4 Upper N 84 2.9
29-sep-2007 Alkaid 1 26.1 Lower 2 35.9
Has anybody used this simple method in order to obtain the latitude, at land or at sea?
Andrés Ruiz
Navigational Algorithms
http://www.geocities.com/andresruizgonzalez
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