Posidonius

0.005 seconds exposure, SBIG ST-6 CCD.
18" f/10.5 Ritchey-Chrétien telescope at prime focus.

Posidonius is a large (95km) shallow crater on the eastern shore of Mare Serenitatus. At high Sun angles, the crater appears as a bright ring. However when the Sun is low, the crater exhibits considerable detail.

Combination of 20, 0.02 second exposures.
SBIG STL-1001E CCD. 20" f/6.8 Dall-Kirkham cassegrain telescope plus a 2x barlow lens.

Combination of 20, 0.02 second exposures.
SBIG ST10XE CCD. 20" f/6.8 Dall-Kirkham cassegrain telescope plus a 2x barlow lens.

Combination of 2000, 0.002 second exposures.
DMK video CCD. 20" f/6.8 Dall-Kirkham cassegrain telescope at prime focus.

Combination of 2000, 0.002 second exposures.
DMK video CCD. 20" f/6.8 Dall-Kirkham cassegrain telescope at prime focus.

The above image was taken several hours after the previous image. It is interesting to see how much the angle of the Sun has changed and the subsequent changes in the shadowing.