|Takahashi FS-78, Canon EOS
0657 Local Time (GMT-8)
|Lunar Eclipse over the Santa Cruz Mountains
31 January 2018
|Several things happened simultaneously on the morning of 31 Jan 2018:
There was a "blue moon" (the second full moon in the same month). The lunar cycle is about 29.5 days. (It can vary between about 29.2 and 29.9 days). So some
months can (barely) fit in two full moons by chance. This is of no astronomical significance. It's just a fluke of our calendar.
Because February has only 28 or 29 days, February can rarely have _no_ full moon. This can only happen in February, and if you think for a minute you will
realize that when this happens the full moons must fall just before Feb 1 (at the very end of January) and just after the last day of Feb (at the very beginning of
March). Since January and March each have 31 days this means that whenever there is no full moon in February there are necessarily two full moons in January
and two in March.
Also the moon's orbit being elliptical rather than circular, the moon is sometimes slightly closer to the earth, making the moon appear a little larger.
And occasionally there is a lunar eclipse.
None of these cycles are related.
By chance all three cycles came together today and there was a lunar eclipse (partial in California, total in Australia), a "super moon" (larger apparent diameter
due to being closer to the earth) and the unusual two full moons-no full moon-two full moons this January-February-March.
The last time all these things chanced to occur together was in 1866.