2011-12-15

Selenelion

This last Saturday, sky-watchers in many parts of the world were treated to a view of the last total lunar eclipse until 2014 [List of 21st-century lunar eclipses - Wikipedia]. I was one such sky-watcher.


Photo beautifully taken in Colorado by Patrick Cullis [Flickr].

Here in Colorado, the eclipse occurred in the early morning hours, just moments before sunrise. That meant there was a chance that I would not be able to see the eclipse before the Moon set. However, that timing also inferred that it might be possible to catch a glimpse of a very rare event: selenelion. "A selenelion or selenehelion occurs when both the Sun and the eclipsed Moon can be observed at the same time" [Selenehelion - Wikipedia].


Considering that a lunar eclipse is when the Sun, Earth, and Moon are in a geometrically straight line in the cosmos, it would seem impossible to see both the Sun and the eclipsed Moon in the sky at the same time. However, thanks to the refraction of light through the atmosphere, the seemingly impossible becomes possible.

I hiked to the top of a nearby mountain before dawn, hoping to see the selenelion, but the Moon dipped behind the mountain range to the West before the Sun began to appear in the East. Hiking beneath the eclipsing Moon had been wonderful and there is nothing like watching the sunrise over a city glistening in snow.


Photo taken by Indy atop Horsetooth Rock in Fort Collins, Colorado.
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