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    Re: Compact Lightweight Metal Sextants - Freiberger Yacht vs. Astra IIIB
    From: John Karl
    Date: 2012 Aug 11, 09:26 -0700

    For those who want the left and right-hand images spread across the whole field of view, you'll get exactly that by using a prism scope with the half-silvered mirror, instead of the Galilean scope. Each image fades out gradually on their far side, just like Jim W. desires. This optics is explained in my book. I particularly like this arrangement the best, but the the disadvantage is that it's hard to find a low power prism scope.

    This works exactly the same with the Freiberger half mirror (half mirror, not half silvered!). I mounted a small co-linear 7x18 prism scope on my Yacht sextant. This is some kind of a sportsman's, or naturalist, scope made by Eagle Optics, about an inch in diameter. As a plus, its color and finish match the sextant exactly, and it fits into the case while attached to the sextant.

    Yes, I agree the vernier is no big deal, but the size and shine of the drum is. But to keep all the math consistent I like to work everything to the tenth of a minute, realizing of course that the final result will likely be off by more than that.


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