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I awoke to a new moon this morning. Well, it wasn’t actually what some [any] astronomers would describe as a new moon. That kind of new moon would look more like the above photo. The new moon I saw is pictured below.
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| THE OWNER OF WEDNESDAY’S GIBBOUS MOON IS AT RIGHT IN PHOTO. |
For any doubters, I used a formula I found on Wikipedia to ascertain that this was in fact a new moon. I’ll paraphrase:
The length of a lunation is about 29.53 days with precise duration linked to many phenomena, such as variation between spring and neap tides. So, d = 5.597661 + 29.5305888610 x N + (102.026 x 10^{-12}) x N-squared where N is an integer, starting with 0 for the first new moon in the year 2000, and that is incremented by 1 for each successive synodic month; and the result d is the number of days since 2000-01-01 00:00:00 reckoned in the time scale known as TT used in ephemerides.
To obtain this moment expressed in UT, add the result of following approximate correction to the result d obtained above:
-0.000739 – (235 x 10{-12}) x N-squared days. Periodic perturbations change the time of true conjunction from these mean values. For all new moons between 1601 and 2401, the maximum difference is 0.592 days = 14h13m in either direction. The duration of a lunation varies in this period between 29.272 and 29.833 days, −0.259d = 6h12m shorter, or +0.302d = 7h15m longer than average. This is smaller than the difference between mean and true conjunction, because during one lunation the periodic terms cannot all change to their maximum opposite value.
NOTE (also from Wikipedia… and paraphrased):
The long-term error of the formula is approximately: 1 cy2 seconds in TT, and 11 cy2 seconds in UT.
So don’t blame me if you try this formula and it doesn’t work.
