by Marek Cichanski
I started around 5pm, when the sky was still blue and there was still plenty of daylight to read my Rukl by. I always enjoy starting a Moon session like that. Just for fun, I set up my lounge-style camp chair and pulled out the 15x50 IS binos. I wanted to see how many features I could identify with binoculars. I mostly used the "Becoming acquainted with the Moon" photographs on pages 20 through 25 of the new Rukl. It was pure 'check-off' observing, no descriptions, just trying to rack up as big of a tick list as I could. Here's what I managed to identify:
1) Maria and 'lakes':
A few lava features on the E limb were visible due to libration:
2) Next, I looked for prominent craters:
(BAF means that the crater was just seen as a Bright Albedo Feature)
3) And a few 'other' features:
| Palus Somnii | Rays from the oblique-impact craters Messier and Messier A in Mare Fecunditatis. (At times I thought I saw both craters, like splitting a double star) |
|---|---|
| Mountains and mountain ranges | Carpatus, Appenninus, Caucasus. |
What a great view! As always, it never ceases to amaze me what can be seen when the image is stabilized. I am beginning to think seriously about trying to use these binos for next year's Messier Marathon. I doubt I could get all 110, but I'll bet that one could get close.
Then it was time for the ED80 refractor on a CG-5 equatorial mount, using 9mm and 5mm type 6 Naglers. These gave magnifications of 67x and 120x.
The 9mm eyepiece gave a really nice full-disc view, which very much emphasized the moon's roundness. It also had a lot to do with the current phase, which is ideal for emphasizing the moon's shape. East of the E edge of Mare Imbrium, all was albedo. Along the terminator, there was a triumvirate of of broad-scale features: First, in the north, there was the great round majesty of Imbrium. This was followed to the south by the crater-burying, and at the same time ray-streaked, plains of Insularum, Cognitum, and Nubium. To the south of this was the battered chaos of the ancient cratered highlands around Clavius and Tycho.
Looking more closely at the Imbrium area, most of it looked as flat as anything can look. I've always been fascinated by the (apparent) Platonic perfection of those plains. People often thought that the Moon had no irregularities, until the telescope was invented. The craters and mountains were just below the threshold of the human eye's resolution. Looking at the apparently perfect flatness of the mare plains through the telescope, we are subject to the same illusion. What, you say? Us? Modern people with telescopes? Yup. That always strikes me every time I see a Lunar Orbiter image, or an Apollo image, whether from lunar orbit or the surface. Those plains aren't really totally flat. They've got little craters and little wrinkle ridges and whatnot.
The craters Helicon, LeVerrier, Lambert, and Timocharis made a prominent quadrilateral of largely-shadowed craters punched into Mare Imbrium. Looked like the constellation Equuleus. I could kinda sorta make out the central crater in Timocharis.
Overall, the seeing during this session was great. Except for a little high-frequency wobble, it was very sharp. A pretty consistent 4 out of 5 in my book.
To my pleasant surprise, I was able to see Hadley Rille from the crater Bela to the crater Santos-Dumont C, and I thought that I could intermittently glimpse the part that runs NE from the N end of Mons Hadley Delta. If so, that was a pretty nice demonstration of the ED80's resolving power. That OTA just continues to score points.
The Montes Pico, Recti, Teneriffe, and the Promontorium Laplace were wonderfully 3-D, with deep black shadows on their W sides. Interestingly enough, the nearby Imbrium ejecta on the N edge of the basin didn't show much of its usual 'hummocky', 'cottage-cheese' appearance. I guess that those hummocks must have considerably less relief than the mountains. Makes sense.
Copernicus looked great. Nice shadows and highlights. The shadow of the 'diving board' had its tip just touching the floor of the crater. Giant scattered hummocks of ejecta to the E of Copernicus were very impressive.
The Montes Riphaeus looked as 3D as I'd ever seen them.
Clavius was beautifully lit. All of the labeled craters that Rukl shows in Clavius were easily visible. The 'radially ridged' structure of the N part of the outer flank of Rutherfurd was just visible - looked just like in Rukl. I could very nearly see every single craterlet shown in Rukl, including the unlabeled ones. Boy, what a great night, what a neat little scope.
Tycho had never looked so much fresher than the craters around it. The other craters in the Tycho region really do have rims that are much less prominent, and which appear 'softer', more rounded, and overlapped by many small craters. Tycho can clearly be seen to be much younger than all of the craters around it. That really started to give me an idea of the vast spans of time visible on the lunar surface. Those ancient craters just sat there after the late heavy bombardment, slowly getting eroded by small impacts, but mostly just looking down implacably for eon after eon. As the earth spun madly around, clouds rushing across its face, continents crawling about like insects, volcanoes popping off like fireworks, seas advancing and retreating like the flapping of a bird's wings, those craters just sat there under their clear black sky.
As always when its visible, the area around Mare Humboltianum looked 'dished in'. The mountains on the far side were sharply etched against the black sky, looking very much like a terrestrial mountain range, with notches between the peaks. I absolutely love looking at mountains on the moon's rim, because you're not just looking down on the mountains, you're looking across at them. It's a much more 'you are there' perspective.
I finished up by looking at the extreme north polar region. I could clearly identify W. Bond, Anaxagoras, Goldschmidt, and Barrow. Additionally, all of Scoresby was visible. At the farthest N that I could see, I think I saw the brightly lit crater rims of Gioja and/or Bond and/or Peary. They looked like enormous, white, vertical escarpments. Like the cliffbands of the Blue Mountains of Australia, but stark white. Awesome.
By then I was cold and sated, and I went inside, and now I'm sleepy.
Posted on sf-bay-tac Dec 11, 2005 05:16:54 PT
Converted by report.pm 1.2 Mar 16, 2006 22:50:22 PT