Quote:
Originally Posted by malloyd
If you adopt that definition, then for all of them to be full the sum of three cosines function would seem to need to be greater than 2.983 (technically some fraction of the time it was might still not qualify, but probably close enough).
Of course if the effect lasts until the end of the night once it happens, instead of never more than 3.9 minutes - the time it takes for Moon A to move through 1/30th of its phase cycle, that's even more complication. Something closer to 1/4 of the time than the 1/27000th you'd get for just the period of phase match.
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I was using a much more generous definition of what counts as full (I have always considered the full moon to last three days). By using a threshold of 2.983, that puts the time between all three moons being full to about once per 200 hours. In addition, there is only a period of about 10 earth years where you get all three moons being full. After that, there is a stretch of about 14 years where it never happens.