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    Re: Clear side of horizon mirrors has reflecting properties.
    From: David Pike
    Date: 2020 Oct 14, 12:55 -0700

    What is an edge to edge enthusiast mean?

    N.B.  This only applies with marine sextant separate artificial horizon observations.  It just means you touch the bottom edge of the straight through Sun or Moon on the top edge of the doubly reflected Sun or Moon, or vice versa.  Such touching is much easier to judge than placing the one Sun or Moon exactly on top of the other, especially with a high magnification eyepiece.  The only problem is you need to be confident which image is which; whether to add or subtract a diameter; and at which stage to do it.  It’s OK if you know where you are, because you’ll spot if your PL comes out a factor of semi-diameter away from your known position.  If you don’t know where you are to start with, you need to be either certain what you’re up to or take a superimposed observation at the same time as a rough check.  If you were doing this every day, you’d soon know what to look for and what works, but if you’re only doing once a year, the ramifications of dealing with the semi diameters soon makes your brain hurt. Well they do me. DaveP   

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