On a whim, I took the Ranger out into the front yard around 10PM, for a tour down the terminator on the Moon. There is something to be said for a telescope and mount that you can pick up in one hand and cart off at a moment's notice (the observing chair is heavier). I did virtually all the viewing at 126X, as the wind was brisk in Palo Alto and the seeing was not especially good.

Up north (chart 20 in Rukl), I found the Dorsum Zirkel ridges interesting. Where it crossed the terminator, it broke into two parallel ridges, and left the impression that something (lava upwelling?) had heaved the two halves apart.

Little craters in the highlands were showing either a brilliantly lit outside of the front wall or a brighter inside of the back wall. In one case the entire circumference was lit up, like a ring. I suspect this variation must have something to do with the local tilt of the particular crater, or perhaps relative position/altitude with respect to the terminator.

Comments, anyone?

One would expect that craters near the terminator, all other things being equal, should have the outside of their sunward wall most illuminated, and as they rotate toward the sun, the back wall should then light up later.

Bulliatus was neat. The crater was placed so that almost exactly half the crater floor was dark and half light, with its crater-shadowline bisecting the central peak. Lighting on the peak itself was reversed from that on the crater floor, with the sunward side bright. The two demarcation lines (light to dark for the peak, dark to light for the floor) were lined up making for a very symmetric pattern.

No doubt the expereience lunatics already know this, but I had not realized how long the shadows can get near the terminator. That of the crater Lambert (I think it was Lambert) was well in excess of the dimensions of the crater itself.