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    Index error by a star-star distance
    From: Andrés Ruiz
    Date: 2008 Sep 22, 16:23 +0200

    I am writing an article about “Index error by a star-star distance”.

    Unfortunately there is not much information about this subject, or I can’t found it. Anybody has any source of information; old books, papers, … ?


    The algorithm is a simplification of the Lunar Distance method, taking into account that there is no semidiameter or parallax.

    The calculated star-star distance is compared with the observed one to obtain the sextant error, that is the index error plus the instrumental error inherent to the sextant.


    For those who want to shoot stars and obtain his IE, the program is available via e-mail under request.

    Feedback is welcoming. My two sextants have a have a negligible error; I can’t check the results for a real significant IE.

    I think the hardest part is to take the distance, is no easy to do this with two stars, and special skills and background is needed.

    A series of up to ten observations are needed in order to obtain the mean UT and Hs.





    The Sextant and Its Applications. William Simms, (free at google books)




    Andrés Ruiz



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