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    Sight averaging (the fit-slope method)
    From: Bob Goethe
    Date: 2015 Jul 20, 14:02 -0700

    >>Thanks so much for pointing out this paper! <<

    Sean,

    It seems that most people with a copy of MS Word have developed their own sight reduction worksheet, and I am no exception.  Given your interest in sight averaging, I thought I would share the portion of my own worksheet that facilitates evaluating multiple sights...and then picking one.  See attached.

    I take sights in groups of four, and I have to get as far as calculating the Hc so that I can come up with a slope for the celestial object, a la David Burch's method.  That Hc is based on the first sight of my four that I take.  If I later determine that the first sight is likely to be accurate, then I am off to the races.  I sort out my Ho, plot it and I am done.

    If, however, I determine that my second, or third, or fourth sight is more likely to be correct, then I use the section of my worksheet that I have attached to this post, and tweak my GHA.  I don't mess with my declination, as it is unlikely to change more than a few tenths of a minute, at most, over the time that elapsed between my first sight and the one I used.  So I don't have to mess with the Hc that I worked up.

    On the attached worksheet portion, I fill in only the line for the minutes and seconds, from the increments and corrections part of the almanac, for the particular sight that I elect to use.  From this, I come up with a revised GHA...which leads me to a revised longitude for my assumed position.  The meridian angle is unchanged, as I say, so the Hc I worked out at the beginning is unchanged.

    Then I work out the Ho from the particular sight out of the four that I selected, and all is done.

    Bob



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