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    Re: Lunars Calculator (ver. 4)
    From: Frank Reed
    Date: 2008 Dec 4, 07:32 -0800

    Dave W., you asked:
    "In the calculator, are the planet distances to center, COI, near, or far?"
    In keeping with traditional practice, the distances are to the planet's 
    geometric center. So when you shoot a lunar using Jupiter, bring the planet 
    to the Moon's limb and split it. 
    Venus is a problem. When Venus is near the Earth, it has a large apparent 
    diameter and also a significant phase. The best approach that I can think of 
    here is to find out the phase of Venus in advance, and attempt to "visualize" 
    the planet's center in the tiny crescent visible with the sextant telescope. 
    Alternatively, you could attempt to make the limbs match and then subtract or 
    add the semi-diameter of Venus from the sight (for Venus the semi-diameter is 
    very nearly equal to the horizontal parallax on the given date since Venus 
    has nearly the same physical diameter as the Earth). Either approach is extra 
    work. It saves a lot of trouble if you just ignore Venus when it's a 
    crescent. That's what I do.
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