Saturday, June 22, 2013

The Superlative Moon

Hello, Shipmates!
By now I have no doubt that most of you have heard some small part of the “Super Moon” hype—at best you’ve been informed that the Full Moon on Sunday night will appear somewhat larger and brighter than usual, and at worst you’ve been treated to the “doomsday” scenarios that connect the “Super Moon” to floods, earthquakes and bizarre weather around the globe, usually accompanied by “photoshopped” images displaying a Moon of ludicrously impossible apparent size, dominating a skyline.

Here’s one now…

Of course, there is no known relationship between the Moon motions and such disasters, beyond the normal effects of the tidal effect that it has on our planet’s oceans and crust; the Moon will be no closer tomorrow night than it has hundreds of thousands of times in the past, and will have no more effect than usual, with the exception that many, many more people than usual will be out looking at it!

So what is happening here, that our companion world will appear up to 18% larger –and 30% brighter—than a normal, run-of-the-mill Full Moon does each and every month (a measure of time that originates in the orbital period of our natural satellite—perhaps we should call it a “Moonth” instead)? It’s quite simple, actually…the Moon orbits Earth along an elliptical path, taking 29 53 days to complete each journey from New Moon through Waning Crescent, First Quarter, Full, Last Quarter and back to New again. Since its path is an ellipse (above) the distance from Earth to Moon varies considerably during the course of a single obit, with the near-point of it’s path (“Perigee”) being considerably closer to Terra than the far (“Apogee”).

It is on those occasions that the Moon reaches that near point of Perigee at a time close to the Full Moon that a “Super Moon” (the astronomical term for this event is a “Perigee-Syzygy” for the combination of a Perigee with Syzygy, or the alignment of Sun, Earth and Moon) occurs in our skies. Of course the Moon reaches Perigee every month, but the effect of a larger-looking Luna is less obvious when the Moon is a crescent- or Quarter-phase, or especially New. Just as importantly, most people hardly notice those less-brilliant apparitions of our natural satellite; the sight of a Full Moon, however, can stop folks in their tracks!

So plan to get outside tomorrow evening and enjoy the Perigee-Syzygy (THAT name will never catch on!). Try to go to a location with a fairly clear Eastern horizon just about sunset; then you can enjoy the sight of our Moon rising above the trees (or water, buildings, mountains, etc.) and the effect of its brightening as the sky darkens. Print out the attached moon map and see how many lunar features you can identify with your naked eye or with binoculars. Got a digital camera? Try taking several photos using Manual settings, adjusting ISO, focus and exposure to get the best image you can.

And as you gaze at our Moon, think about what you are seeing. You are looking at another world, the only body in the Solar System that we can regularly study without benefit of a telescope, without special filters, and still perceive actual details of its surface. And the only celestial body that bears human footprints—that members of our frail, troubled species have actually walked upon its surface. More than that, without the Moon, it is very possible that we wouldn’t be here to enjoy our view of and to ponder our relationship to it.

So show Luna some respect, and look up more often—you may find that our Moon is always “Super”.

Tom Epps
Operations Chief
USNS Alan Shepard

P.S. Announcing the "Super Moon" photo contest: send me your best picture of Luna, and tell me of your experience…I'll post the best of them here.


  1. you say "Perigee-Syzygy" I say Mxyzptlk (or for those Old-Schoolers reading this: Mxyztplk)...

  2. Thomas L. Epps5/29/2015 11:15:00 AM

    Oh, whatever you call the little imp, he's just Rumplestiltskin in a purple costume!