Saturday, October 24, 2015

Lunation 195: The 11-Day-Old Moon

My photographic project continues as I "shoot the Moon" every night at approximately the same time (Midnight, Universal Time), posting my best results the next morning. Today we are three days into our month (or "Moonth", if you prefer) of Lunacy, and Luna is 11 days "old", or 11 days past it's New phase.

So, what is a "Lunation"?  A Lunation, or Synodic Month, is the amount of time it takes for the Moon to travel in it's path from one New Moon to the next.  Due to the inclination of our satellite's orbit relative to Earth, that orbit's elliptical shape, and the effect on the Sun's gravity upon the Moon's motions, this is not a fixed value; it can vary from 29.26 to 29.80 days, with an average time of 29.53 days.

Because the Synodic Month varies in duration as compared with our Gregorian calendar, the dates of phases (Full, Quarter, New) also vary from calendrical month to month.  One result of this is that we aren't able to simply look up at the Full Moon and determine the date, as in "Well, there's the First Quarter Moon, so it must be the 14th".

Along with the latest result of my photographic effort I am including a fairly basic lunar map; go outside tonight and see how many features you can identify on the Moon's surface with your unaided eyes, and then with a pair of binoculars.  If it is cloudy this evening (as I expect it will be, here in coastal Virginia), then compare the map with my photos to date; how many Maria ("seas") and craters can you find?

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