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    Re: Unexpected USNO height correction precepts
    From: Frank Reed
    Date: 2018 Dec 27, 12:23 -0800

    While looking at the sky here a moment ago, it dawned on me that the rule I gave for the Venus offset disagrees with the one that I have used before. I wrote:

    That distance is given to good approximation by a simple expression which is 90% of the semi-diameter of Venus, and since Venus (at the cloudtops) is about 96% of the diameter of the Earth, the SD of Venus is about 0.96·p (p for parallax of Venus), so we have 
       S = 0.86 · p.

    Instead, I suggest using (as I have previously) the SD of Venus minus a tenth of a minute:
       S = 0.96·p - 0.1'.

    Sorry for the confusion!

    Frank Reed

       
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