The image below shows the western part of Mare Frigoris. The date and time (UT) are in the file name. I took this using my C11 and Celestron Neximage 5 Solar System Camera. This image is a stack of the best 15 out of 135 frames processed first in Registax 6 and finished in Photoshop Elements 9. The sky that night was mostly clear, unseasonably warm, humid and a bit hazy. Transparency was 3rd magnitude and seeing was 7-8/10.
Mare Frigoris is the arcuate, flat, gray plain extending 1,446 kilometers end to end running north of Mare Imbrium in the west and the crater Plato to north of Mare Serenitatis in the east. Mare Frigoris means “Sea of Cold” and covers about 436,000 square kilometers, an area roughly the size of the Black Sea. Its formation is a bit uncertain and the eastern and western portions appear to have developed in different geologic eras. Wikipedia considers Mare Frigoris to be the outer rim of the ancient Procellarum Basin, of which Oceanus Procellarum is the remnant visible today in the northwestern part of the Moon. The Rukl “Atlas of the Moon” and J. Kelly Beatty’s “The New Solar System” show Mare Frigoris (or at least its western part) as the outer rim of the later Imbrium Basin formed by an impact 3.85 billion years ago. This basin, like the Nectaris Basin on the Moon’s near side and the Orientale Basin on the Moon’s far side contain a central depression surrounded by uplifted mountainous rings with narrower depressions in between the rings. These depressed areas within the basins gradually filled with basaltic mare lavas over the next roughly half billion years.
Jay Albert, February 12, 2014