NavList:

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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