June 24, 2019

29.9.9: Can you Spot the Cave in Copernicus?

I’ve got a unique challenge for you, as you brush up on your lunar geography in anticipation for next weeks’ LCROSS impact. Next time you’re viewing the waxing gibbous Moon with your friends, amaze them (or make them think your totally crazy) by issuing the off-handed remark; “Did you know that there is a ‘cave’ in the crater Copernicus? The “cave” in question is, of course, an optical illusion. Its interesting to note, however, that in the pre-Apollo era, would-be Selenographers were faced with a lunar landscape that was much less straight forward. This first came to our attention while reading a February 2003 article in Sky & Telescope written by Steven O’Meara. The cave itself rests on the northern inner lip of the crater and is elusive unless caught at the precise sun-angle of 10.7 degrees above the local lunar horizon. This generally occurs around 10-12 days of age, and I encourage you to take a look early this week. [Read more...]