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On page 4 of the almanac, there is a table of moon phases, with dates, and
time in hours and minutes.

On the daily pages the lower-right corner of the right-hand page has upper
and lower meridian passage times, age in days, a percentage (of surface
lighted?) and an image.

I am not certain how the moon diagrams in the lower hand corner of the daily
pages are correlated to time.

My best guess is that the percentage-lighted figure is for 12:00 UT.

I arrived at that by looking at moon phases and times on page 4, and picking
several that were closest to 12:00 UT.  I chose those closest to 12:00 as
the rate-of-change of percentage visible appears to be nonlinear compared to
time, so I wanted to minimize that effect.  In the specific example of of
first and last quarter I observed a 9-11% range-of-change per day, nominally
.42 percent per hour.  Multiply that figure by the time difference between
the time stated on table 4 and 12:00 the result agrees with the percentage
figure in the daily pages.

I have made the assumption that time stated for a phase on page 4 is the
precise time (to the minute) when the moon is completely dark, 50%
dark/light, and 100% light.  And assumptions often get me into trouble.

Can anyone confirm or deny my assumptions regarding:
1.  Page 4 moon phase table
2.  What time the percentage figures on the daily page reference?

Thank you,

Bill

   

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