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    Loss of accuracy using Sun over Sun with a mercury artificial horizon?
    From: David Pike
    Date: 2016 Jul 18, 00:57 -0700

    It’s easy to see why edge shooting and semi-diameter are used when shooting the Sun against a sea horizon, but is it so necessary when using a mercury AH?  You’re not trying to guess the centre, just place one circle over another.  I appreciate that the Sun doesn’t always appear as a perfect circle, especially at low altitudes, so that might present a problem, but on the other hand, you’re excused trying to remember, possibly in a stressful situation, if the semi-diameters should be added, subtracted, multiplied by two, or divided by two.  Has anyone any experience of how much accuracy is lost using Sun on Sun compared to edge on edge with an artificial horizon?  DaveP

       
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