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Crisium at Lunar Sunset

Jane Houston Jones


Sunrise on Mare Crisium occurs when the waxing moon is new and the morning light washes over its features. But sunset is happy hour on Crisium. The waning moon phase, high overhead in the late evening and early morning hours, is when Mare Crisium takes on a life of its own. It rivals some of the other "Oh Gosh" lunar features.

Mare Crisium transited well after midnight on the morning of March 1, 2002. Mojo and I wanted to spend a while observing lunar features including the amazing Crisium tonight, while the moon was high overhead. We set up our Astro-Physics 105mm f/6 Traveler on the back deck at dusk and settled in for a long nights journey through the solar system. A few feet away from the Traveler sat a telescope of a different color. It was my clunky, red 10 inch f/7.3 homemade reflector, with a six foot cardboard tube and a hunk of drainpipe which serves as a focuser. There aren't many more different telescopes than these two.

While waiting for the moon to transit (and thus clear the trees and roof top) we observed Jupiter, the red spot, then a large red barge in the NEB in both telescopes. The colors were much more vivid in the larger aperture telescope. The red barge was really a bright red through the 10 inch. We looked at Saturn, too, but it is getting low, and the views were not anything to write home about tonight. Seeing conditions were soft, but heck, we have a new Zeiss binoviewer and matching sets of Zeiss Abbe Orthos and we were happy to have some decent weather for a change to try them out.

The set of six ZAOs range from 4mm to 34mm, offering a range of magnification from a low of 17x to a high of 152x in the Traveler and 54x to 463x in the reflector, without barlow. We tried many of them in the Traveler, and settled for a pair of 6's, yielding a satisfactory magnification of 101 times. I used the 10mm for 185x in the reflector. They are truly amazing eyepieces.

There were so many fascinating lunar features to view, and at 2:00 a.m. we started observing the moon in earnest. Mojo really enjoyed the bright twin rays of Messier A, and the Tycho, Copernicus and Kepler splats. Then we both concentrated on the shores of Lake Crisium. The wrinkle ridges of Dorsa Tetyaev and Dorsa Harker on the eastern shore were sinewy and prominent, even though the sunset terminator was lapping at the shores like a receding low tide on the beaches of earth's own ocean.

On the north-western side of Mare Crisium we noted the wrinkle ridges Dorsum Oppel. These ridges inside Mare Crisium really do appear to resemble a continental shelf or ledge surrounding the sunken sea. The few craters on the floor of Mare Crisium were brilliant in the unfamiliar light. The craters which nestle up near the sea wall, such as the partially sunken or flooded Yerkes and Lick (kciL in the refractor) caught our attention, and I know I'll want to return here and view these features again with a sketchpad handy.

It was a lot of fun to observe this familiar lunar feature in a totally unfamiliar light.


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