Friday the 13th and the Harvest moon

Let’s set the record straight about Friday the 13th: It’s not rare. You cannot have a year that doesn’t include a Friday the 13th. Some years like this one have two (September and December), some have three (last year, and again in 2015) and, rarest of all, an occasional year like 2014 has only one. So, bad luck is a finite commodity.

The Harvest Moon is much more variable in position and date of occurrence, since it can even happen in October. However, it never looks different from other Full Moons. Its calling card is simply that, for several nights in a row, it keeps rising around dusk.

Instead of the usual one-hour delay in successive moonrises, next week we’ll see the Moon come up just 20 or 25 minutes later each night. Start watching as twilight deepens on Tuesday. There’s the almost-Full Moon low in the east.

Next night, Wednesday the 18th, is the night of the Harvest Moon. Again it’s low in the east at dusk, having risen just before sunset. The next night – Thursday, right after sunset – there it is again, having popped up minutes earlier. You can’t get rid of this Full Moon. It’s the relative who came for dinner.

Sure, it might look orange and enormous when it’s low. But all Moons do that. Nothing differentiates a Harvest Moon visually.

It’s the polar opposite from the Full Moons of February, March and April. Then you’ll see moonrise at sunset one night, but wham! There’s an hour-and-a-half delay until the next night’s moonrise, and another hour-and-a-half delay the night after that. Result: A 7 p.m. Full Moon rise is followed, just two nights later, by the absence of moonlight until 10 p.m.

You can see why this is called the Harvest Moon: Just when the farmer runs out of daylight to finish harvesting work, the Full (or nearly Full) Moon shines down from the sky night after night, to help out with extra light. This doesn’t happen at any other time.

Thus, the Harvest Moon is an “effect” rather than a visual oddity. It has to do with lunar behavior, not appearance.

One more note: The exact moment of the Full “Harvest” Moon is 7:13 a.m. on Thursday the 19th. That’s 24 minutes after it has set. But since days switch over at midnight, many in the media will get this wrong – count on it – and say that the Harvest Moon is the 19th and tell you to go out that night, Thursday night.

So let’s be clear: The nearest night to the Harvest Moon is Wednesday night. If you look up at around midnight, you’ll miss the moment of Full Moon by seven hours. If instead you go out on Thursday night and observe at midnight, you’ll miss the moment of Harvest Moon by 17 hours. It’ll appear decidedly out-of-round.

Clear enough?



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