There is a formation of four craters that when illuminated "just so" forms a fairly distinctive X on the moon's terminator. I'm trying to find out how often it's visible, don't think it's every month.
http://the-moon.wikispaces.com/Lunar+XAnyway, it was pretty cool seeing it appear. I started looking about 19:15GMT and could see two of the legs of the X, at 19:45 the others were barely visible. After tea, it was very clear, although the dew had come down and fogged up my eyepiece somewhat. What was most cool was the undeniable fact that I was watching the effect of the sun rising on the moon, at about 1/28th the rate on earth. Not quite as impressive as the time I saw the dark edge of the moon suddenly blot out a star as it passed in front. That really gave me a sense of how things are moving up there.
http://the-moon.wikispaces.com/Lunar+XAnyway, it was pretty cool seeing it appear. I started looking about 19:15GMT and could see two of the legs of the X, at 19:45 the others were barely visible. After tea, it was very clear, although the dew had come down and fogged up my eyepiece somewhat. What was most cool was the undeniable fact that I was watching the effect of the sun rising on the moon, at about 1/28th the rate on earth. Not quite as impressive as the time I saw the dark edge of the moon suddenly blot out a star as it passed in front. That really gave me a sense of how things are moving up there.
