Tic Tac Toe on the Moon

by David Kingsley


At 3:06 PM -0800 1/2/01, James Turley wrote:

8": Sunrise over Cassini in the Lunar Alps. Shadows cast in A and B central craters.

Sounds like you guys had a very fun night up there.

When you looked at the moon, did you happen to notice the beautiful game of Tic Tac Toe being played out across the terminator last night?

I set up near home in Palo Alto and looked at the moon about 8 pm. The western edge of crater la Caille was brightly lit near the terminator. Right next to crater la Caille, the high eastern edge of the crater Purbach also caught the sun, although the crater itself was in darkness. The sun hitting just the highest rims of these two adjacent craters made an almost perfect, brilliantly white X shape, scrawled right at the boundary of the white and dark halves of the moon. The beautiful figure X sat in a perfect diagonal row with two well shaped, bright-rimmed O shapes (craters Werner and Aliacensis). The X and two O's together looked just like a diagonal from a giant Tic Tac Toe game being played out across the surface of the moon.

Neat sight! I spent some time sketching it and watching other bright peaks blink on in the darkness just beyond the terminator. Didn't get any deep sky stuff done, but it was a very enjoyable short session near home.