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    Re: Sextant accuracy (was : Plumb-line horizon vs. geocentric horizon)
    From: Frank Reed CT
    Date: 2005 Feb 12, 07:38 EST
    Alex, you wrote:
    "after long practice I can achieve 0.2 to 0.3 accuracy most of the time,
    with my 7x scope, both for lunar and star-to star distances."
    Interesting. I remember you were puzzled by the star-star distances a couple of months ago. Are you saying that they have finally fallen in line to your satisfaction?
    "my common mistake in the beginning was to observe
    very bright Moon. It obscures the star. One has to use
    a filter, sometimes two, on the Moon, so that the star is
    well visible when it touches.
    Same applies to a pair of stars where one is substantially brighter.
    In general, better results with star-to-star distances can be
    achieved with stars that are not very bright. Same applies to index
    check with stars: use a weak star."
    Aha. That makes good sense. Myself, I'm always fiddling with the filters until the images are as "dot-like" as possible. A bright star inevitably has a dazzling halo of little rays around (these are formed in the eye if I understand correctly (?)) which makes it difficult to decide just where it is in the visual field.
    42.0N 87.7W, or 41.4N 72.1W.
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