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Hewitt S., you wrote:
"Wow, what a spectacular photo of the moon's far side. The crater in
the middle looks to be about 1/6 the moon's diameter and deep, deep,
deep."

Yeah, that's Mare Orientale. The photo was taken about ten years ago by the 
Cassini probe which has been orbiting Saturn for the past four years. There 
are very few photos that show any portion of the Moon's far side as a nearly 
full hemisphere.

Mare Orientale is actually right on the dividing line between the near and far 
side, and it is in fact very deep. Now, all of this might sound off-topic for 
NavList, right? But amusingly enough, there is a connection for those crazy 
lunarians (like me) who try to get everything accurate to the smallest 
fraction of a degree. Since Mare Orientale sits right on the dividing line 
between the near and far hemispheres, the depression makes a slight "dent" in 
that section of the lunar limb. The moon is flattened there. So if you 
measure a lunar distance to a star that happens to be in the right direction 
--such that when you bring it to the Moon, it lines up with Mare Orientale-- 
then the measured lunar distance will be slightly larger than predicted. Note 
that this depends on the "lunar librations" so sometimes it would matter, 
sometimes not. For the record, we're only talking like two arcseconds...

-FER
http://www.HistoricalAtlas.com/lunars




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