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    Re: Lunar distance this Sunday
    From: Frank Reed
    Date: 2017 Apr 16, 19:48 -0700

    Here's what I've got so far... Just entering dates and checking lunar distances (at noon Greenwich on the date in question), for the period from 1997 through 2021, I find that the maximum lunar distance (which occurs when Easter happens right after the Full Moon) is 173°, the minimum (when Easter Sunday fall a full week after Full Moon) is 89°, and the average is 132°. Those numbers are bound to change a bit when we look at a larger set of dates, but they're a start. 

    Some useful (?) inputs on the question: the vernal equinox is March 21 by definition for the purpose of determining Easter. The "paschal full moon" is determined by an algorithm that approximates the first full moon after the equinox, but apparently it can be as much as two days before the actual full moon or two days after. How often does that occur? Since the actual full moon may occur two days after the defined full moon, it is, in fact, possible for the moon to be waxing (for one more day) on Easter Sunday, despite the formal rule. In addition, the paschal full moon is a full calendar day, not an instant of time like the standard definition of the astronomical full moon. That complicates matters slightly.

    Things are different for eastern orthodox Easter dates, and the max, average, and min LDs are all smaller by about 49° for eastern Easter. So if anyone should ever ask you what the difference is between western Christianity and eastern Christianity, you can answer "about 49°" and happily walk away.

    Frank Reed

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