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    Re: Star to Star Distance Sextant Calibration
    From: Michael Bradley
    Date: 2019 Apr 11, 15:39 -0700

    Andre, you wrote:


    if I did not misunderstanding the data, it was:
    The data is for 20:00:00 UT 08/04/2019. I mislead you by not putting a fully defined UT into the spreadsheet. My apologies, an improved version of the spreadsheet is attached.
    Put that into any planner, with the EP, and you'll get the sky view at the time of the distance measurement.
    Because the celestial sphere has rotated only 1 degree from one night to the next, you can put in the wrong date by 1 day and the calculator will give an answer identical to the correct one in most cases. And the observation result can be expected to almost identical. The shape and size of the star sky image doesn't materially alter from one night to the next.
    No horizon is required.  The Altitudes H1 and H2  are required only for calculating the refraction, and using Hc from a planner will be OK.
    The sight can be taken any time the targets are visible and have altitudes between normal comfortable and accurate observation limits, say 15 to 60 degrees. 
    In the calculator the spreadsheet uses sha for the two stars instead of LHA - we only need the difference between the two angles, the two identical values of gha Aires will cancel out.
    Happy navigating
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