Lunar X

April 01, 2012

Lunar-x

Photographer: John Chumack; John’s Web site
Summary Author: John Chumack

On the night of January 30, 2012, I was imaging Jupiter and decided to swing my telescope over to the Moon for a quick look and immediately noticed the Lunar X staring me in the face. The Moon was just about at first quarter phase, which is the best time to see the Lunar X. This is a famous optical feature on the Moon, which appears like the letter X when the terminator is at an optimal position. It’s an excellent example of how the combination of lighting and topography can often combine to produce a pattern that repeats on each lunar cycle, but only for a short time. The illusion of the X is created by sunlight falling on the rims/ridges between the craters La Caille, Blanchinus, and Purbach. The resulting X is observable for about four hours -- but only just prior to the lunar first quarter.

Photo details: 10 inch Meade SCT Telescope, DMK 21AF04 Fire-wire Camera; 2x Barlow lens for close-up but no Barlow for wide angle image; 1/30 second exposure; 400 frames stacked in Registax 6. Photo taken from my backyard observatory near Dayton, Ohio on January 30, 2012, around 7:45 p.m. (local time).