Sunday, November 22, 2015

Lunation 196: The 10-Day-Old Moon

When I observe Luna (with the naked eye and binoculars while at sea, and with telescope on land) I am always struck by how different it can look from hour to hour and day to day.  Not simply the change of phase as the Terminator creeps slowly across the Moon's face, constantly revealing or concealing seas, craters and mountain, but other effects that affect what we can see as we gaze at our natural satellite.

There is the effect of weather.  I have found that profound changes in apparent brightness and hue can occur with only a thin layer of cloud or haze between our eyes and Luna; even greater effects can be observed soon after moonrise (or just before moonset), those times when we stare through the thickest atmospheric "filter".

Then there is the Moon's Libration. This is an effect of the elliptical orbit of the Moon; its shape and tilt relative to Earth result in an apparent wobble which, from our perspective, brings tantalizing glimpses of a small area of that part of Luna that we normally think of as its "far side".  Libration changes what we see of our Moon in subtle ways, but the differences are there.  Check out this terrific video on the subject at...

So the Moon always looks different.  And that's why I find myself drawn to it; why after 45 years spent exploring craters Tycho, Clavius, and Petavius, "moonwalking" Mare Imbrium with optical aid and imagination, and exploring Valles Alpes and the Straight Wall at extremely high powers when the weather allows, I am still captivated by it's light and landscapes.  

After all, the Moon is another world.  The only one which we can explore in detail without the expensive requirement of a space program, and the only one where human beings have walked and wondered at its "magnificent desolation", to quote Edwin "Buzz" Aldrin, the second man to walk its surface.

Based upon my own study of our satellite, I tend to think that "Buzz" summed it up perfectly.

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