Good Librations

by Matt Tarlach

Favorable libration has made for good views of the SW limb over the past few nights. Wednesday with the terminator near 75d I had the best view I can recall of Bailly. Under good conditions the rim shows all the way round in great relief, with tons of detail on the floor, far more than plotted in Rukl (viewing w/ 7" mak). The rise in the center is lumpy and pocked, and close to circular, revealing Bailly's nature as a miniature multi-ring basin. I didn't think to look for the outer ring....before learning of the favorable libration I had indulged in some favorable libations, and my viewing session was quite relaxed. :)

Last night, Thursday, I was a bit better prepared, though due to issues with the mount for the new 7" I observed with the old 127mm Orion. With the terminator at 87d, Hausen came into view behind Bailly. When the Moon first rose to viewing height the top of the west rim and central peak of this large, fresh crater shone brightly off the limb of the Moon; as I returned to it throughout the evening the West rim merged with the rest of the crater, and the first great terrace became visible.

To the north of Hausen, Orientale really put on a show. Light was fairly high on the Cordillera but a thin line of shadow remained to set them in relief against the lunar surface. The limb was tipped far enough toward us that the range appeared clearly arcuate. The crater Schluter astride the northeast rim of the Cordillera was an impressive object, and the dark mare of Lacus Atumni behind the range contrasted nicely with the bright surrounding plain. A heavy line of shadow separated the inner and outer Rooks...early in the evening the inner Rooks looked like a bright line drawn sloppily in the blackness off the limb. West of Eichstadt there is a wide, hilly "pass" through the outer Rooks. Under very low light the area beyond, below the peaks of the inner Rooks, was speckled with bright spots - perhaps a blocky debris field.

Good librations continue tonight; if the clear weather holds I'll be back at Orientale, hoping for Maunder, Hohmann, and Kopff, and perhaps the dark floor of the Mare itself....libration is also better than average for the southeast limb.

Posted on shallow-sky Mar 25, 2005 07:45:47 PT
Converted by report.pm 1.2 Mar 30, 2005 19:46:55 PT