Sunday, April 22, 2007

20070421 - Details of the 4 1/2 day crescent moon

Session name: 20070421.1730

After a day Moon advanced eastward in the sky, leaving Venus further behind. With the bold punch that Venus delivers, most people noticed her even in daylight. Noting the separation of Venus and Moon, figured it was a good time to calibrate my thumb-to-pinky angular distance. With arm outstretched, it was a *perfect* fit from tip to tip. I guessed 21° for my hand and Charlie said 22 ½° for his. Checking Planetarium for the Palm, the angular separation was 21°27'.

Between sharing veiws with the passersby, Charlie and I would get some eyepiece time with a young crescent still holding the old moon. In the scope, we observed Grimaldi, Aristarchus, Mare Frigoris, and Mare Humorum in the earthshine. Copernicus and Kepler were not as easy as I thought they could be. Of the two, Kepler may have been spotted with much less confidence in Copernicus; the same with the Lakes near Mare Orientale. I'm not certain but believe these to be libration features. I thought I could see them but Charlie mentioned that libration was favorable on the eastern limb. Lo and Behold! Mare Marginis & Mare Smythii were both very well turned over our limb becoming nearside. I noted crater Endymion and but didn't spot Mare Humboldtianum. Along Moon's southeastern limb I was unsure if I saw Mare Australe. With libration so favorable to the east, the lakes bordering Orientale could not have been seen.

Two sets of mountain, Montes Secchi & Montes Pyrenaeus drew the eye into the central region of the morning terminator, providing borders to Mare Fecunditatis and Mare Nectaris. A large, irregular-shaped crater, Gutenberg, is an interesting crab claw-shaped crater, its northeastern wall collapsed.

The floor of Mare Nectaris was fantastic in tonight's light. One could see rings of arcuate ridges possibly revealing the rings of the basin. This was my first time noticing this effect. I counted three rings of the ridge effect and lastly a crumbled eastern wall, the lunar Pyrenees Mountains, circumscribing them.

Two valleys in the central and southern regions couldn't escape our attention. Vallis Snellius & Vallis Rheita are unmistakable as large, wide valleys cutting a straight groove in the lunar landscape. The Sun's angle today provided reasonable relief. Yesterday's observation left and impression of a sharp cut into the terminator. Quite possibly this was Vallis Snellius in the terminator.

In the park, spring is here. Green grass carpets the field before us. Trees surround us on all sides. Pollen irritates my wife's sinus. Birds fly from tree to tree, red robins stand their ground. People walk, talk, and play. Charlie stands next to me. I look through the eyepiece at the grayish, whitish lifeless world of Moon. It is hard to imagine that there once was a time when Life did not exist on our planet. I wonder if it was color that give birth to Life?