Moon, 1/28/04

Rambling amongst lunar mountains and lakes

by Marek Cichanski


I couldn't wait to get home today and look at the moon. I knew that it would just be visible in the slit of sky that I see from the back porch of my apartment, if I rushed home from work and set up my scope. So, I finished my afternoon lab (teaching people how to identify rocks), and jumped on my bike. Pushed the pedals moderately hard, in order to get home and look at more rocks - a quarter of a million miles away.

This moon session lasted from about 18h to 20h PST. Seeing was about 3.5 out of 5. Seeing was mostly what I call "long wavelength" turbulence, which is much better than "short wavelength" turbulence. In the case of the former, you can still see fine detail, it just waves around. In the case of the latter, the fine detail is fuzzed out.

Started out with the 16mm T5 Nagler on the M603. This is a great eypeiece / scope combo for full-disc sightseeing on the moon. Later, I looked at smaller features with the 9mm T6 and the 5mm T6. Started by cracking open Rukl to the photographs entitled "Becoming acquainted with the Moon - The Moon at First Quarter." Ahh, so good to be back with the good ol' moon...

The moon was very nearly at first quarter tonight, with the terminator just about right down the middle of the disc. At the end of my session, I worked on estimating the seleographic colongitude as accurately as I could - more on that anon.

I started with features on the eastern limb. It looked like I was seeing patchy mare material of Mare Marginis and Mare Smythii. I haven't checked VMA yet, but I'd guess that the eastern limb was librated towards us tonight. I think I could distinguish both of these maria. Some of Mare Australe also appeared to be visible. The craters Langrenus and Geminus stood out as bright albedo features, but without any real shadow detail. I found a new game - looking near the limb of the moon and trying to spot the feature that shows a shadow, while being as far from the center of the disc as possible. I was surprised how far east I could still see shadows. The craters Bilharz, Naonobu, and Atwood were about the easternmost things (60deg E) that showed much shadow.

Proclus and the Palus Somnii were well seen; this part of the moon is a perennial favorite of mine.( I saw it on the day I met TAC, one spring evening up at Montebello in 2002. I think I saw it through James Turley's 4" Vixen refractor, and Rich Neuschaefer's AP 155. This was my first-ever encounter with: 1) a 2" eyepiece, 2) apochromatic refractors, and 3) a binoviewer. From then on, I've been doomed...) Some Proclus rays were visible on Mare Crisium, which I'd never really noticed before. The bright pair of rays extending westward from Messier A was also nicely visible.

The first lake I saw tonight was Lacus Spei - the Lake of Hope. I really enjoy the lunar lakes; they're one of my favorite things about Rukl. I have never learned them well enough to anticpate them. Instead, they are always nice little treats that find when I'm working through an atlas page. And they always have such wonderful names!

This was a good night for Mare Nectaris. It holds a special interest for me, because it is the oldest of the nearside basins. Its heavily fretted and degraded margins attest to this, contrasting with the fresh, mountainous rims of Serenitatis and Imbrium. The Rupes Altai is the one prominent shock-ring feature that remains from the ancient Nectaris impact. It was glowing brightly in the morning sun tonight, as it always does around first quarter. I thought that I deteced hints of other concentric structure between Rupes Altai and Nectaris - subtle, low, curving ridges, heavily overlain by craters. Hard to say if they were real or just imaginary. On the western side of Nectaris, the craters Theophilus, Cyrillus, and Catharina were awesome. A real sight to behold. Fun to play around with the relative ages. I think that Catharina is the oldest of the three.

Then it was off to the northeastern limb, where the crater Endymion was a strong contender for the easternmost shadow-bearing feature. Hmm, what's that little patch of mare to the northeast of it?...why, that's Mare Humboltianum! This was something really neat to see. Mare Humboltianum is sort of the 'Mare Orientale of the eastern limb'. It's not as big or rugged as Orientale, but it lies between 75 and 90deg E, so it's basically a libration-zone feature. It seemed to me that I was seeing terra material all the way around it, but I had a hard time picking out particular craters around the mare. I could make out Endymion B and C, and I think I saw Hayn, but things got pretty tough around 80deg E. Couldn't really distinguish Belkovich. It seemed to me that the figure of the Moon seemed "dished in" in the area of Humboldtianum, as though it lay in a deeply sunken basin. How much of this was real and how much an effect of seeing this small dark patch near the bright limb, I can't really say.

I love Rukl's description of Mare Humboltianum: "Madler gave Humboldt's name to this formation because he recognized a symbolic parallel between Humboldt's explorations of unknown terrestrial continents and the way that this lunar mare seems to form a link between the known and the unknown hemispheres of the Moon." Very cool.

The area around the craters Eudoxus and Aristoteles ROCKED! This is something that I absolutely love about the northern high latitudes of the moon's eastern hemisphere. The ejecta (Imbrium ejecta, I assume) has what I call a "pebbly" texture. I've probably mentioned it in previous ORs - it looks like spray-on wall texture. What enormous blocks and hummocks must characterize the lunar terrain in this area! It looks a lot like MOLA images of the 'sulci' around Olympus Mons on Mars, which are vast hummocky landslide deposits, or like the similar submarine landslide deposits around the Hawaiian Islands. Exquisite!

I swear, a good night of lunar observing is about as good as it gets. Looking at stuff like this through a nice scope, on a night of good seeing, in a nice big Nagler eyepiece, is pure luxury. It reminds me a lot of what John Muir said about Cathedral Peak. Now, if you've ever been up to Tuolumne Meadows, you'll have seen Cathedral Peak. It's a beautiful, pointy, sawtoothed mountain that lies SW of Tuolumne. In "My First Summer in the Sierra", Muir summed it up in one of his many memorable passages:

"I never weary gazing at the wonderful Cathedral. It has more individual character than any other rock or mountain I ever saw, excepting perhaps the Yosemite South Dome. The forests, too, seem kindly familiar, and the lakes and meadows and glad singing streams. I should like to dwell with them forever. Here with bread and water I should be content. Even if not allowed to roam and climb, tethered to a stake or tree in some meadow or grove, I should be content forever. Bathed in such beauty, watching the expressions ever varying on the faces of the mountains, watching the stars, which here have a glory that the lowlander never dreams of, watching the circling seasons, listening to the songs of the waters and winds and birds, would be endless pleasure."

Substitute Moon for Cathedral Peak, and 'celestial object' for 'rock or mountain', and you've got my take on my favorite object in the sky. Game, set, match. Rock on, J.M.! (and if you've ever hiked around Cathedral Peak, you'll know what he was on about...)

Next time you're looking at the moon around first quarter, check out the patch of highlands material between Maria Tranquillitatis, Fecunditatis, Nectaris, and Sinus Asperitatis. It's a remarkably distinct 'island' of terra in the midst of all these lava plains. Its most prominent crater is called Capella. If the moon were like Mars, with both the 'land' and 'sea' regions receiving names (e.g. Noachis Terra, Mare Erythraeum), it might have been called Capella Terra. That would have been kind of neat. It has a couple of rilles in it but I couldn't quite see them. It contains the crazy-bright craters Censorinus and Censorinus A. These are some of the brightest small craters on the moon. (They are probably bright because they're young; freshly ejected material is rugged and relatively porous, scattering light very effectively and making young craters look bright. I'll bet these craters prompted much unwarranted speculation by the 'endogenists', who tried to ascribe internal, volcanic origins to all sorts of impact features. Probably drove poor Gene Shoemaker nuts back in the 60s. Some folks still bend over backwards to find some sort of little volcanic gewgaw somewhere or another on the moon. As if vast seas of frozen lava the size of entire western states just wasn't enough... Okay, snippy fit over...) At any rate, "Capella Terra" is neat.

I spent a lot of time looking at the area of Rukl chart 23, around the southwestern edge of Mare Serenitatis. More cool mountains! The Montes Haemus are named for a mountain range in the Balkans - which itself means 'mountains'. There was an unnamed peak between the crater Bowen and the main crest of the Haemus range that was just awesome. It was an incredibly huge, wedge-shaped mass, with its southeastern edge lit up by the sun, while it cast a coal-black shadow off to the northwest. Utter massiveness. It reminded me of George Mallory said about the first view of Everest in 1921: "A prodigious fang, excrescent from the jaw of the world." Rukl doesn't give it a name, but it was really impressive. The Haemus range farther NW was also very bulky and impressive, reminding me vaguely of a map-view outline of the Diablo Range.

The 'lakes' on the southwest side of Montes Haemus were a delight to observe, both in the scope and in Rukl. First, I noticed Lacus Odii on the chart - the Lake of Hate. Whoa, now there's a name for you. Couldn't quite make it out, though, but I could see Lacus Doloris quite clearly - the Lake of Suffering. Whoever named these features wasn't holding anything back. In contrast, the adjacent lakes were Lacus Lenitatis and Lacus Gaudii - the Lakes of Tenderness and Joy. What a panoply of emotion! And best of all, there's an isolated mountain peak right between all three. What a mountain that would be to climb, and to sit on the summit with map in hand. Maybe someday this peak will be in the Emotional Lakes Wilderness Area ;-)

(These evocative names brought to mind the names of the mountains in the North Cascades. There is no finer range on the continent, both in terms of rugged scenery and marvelous names...Forbidden Peak, Mount Triumph, Mount Despair, Mount Formidable, Mount Challenger, Isolation Peak, Desolation Peak, Mount Fury, Mount Terror, etc...)

There were a few other features, but that was most of the detailed work. One last thing that I finished up with was to try to estimate the selenographic colongitude of the sun at about 10 minutes before 20:00 PST. If I understand Rukl's explanation of this, it was about 356.5deg, (i.e. at a lunar longitude of 3.5deg E). It was well marked by being at:

1) the center of the crater Abategnius, and 2) about 3 crater diameters E of the eastern edge of the crater Triesnecker.

That was about it, besides general gaping and oohing and ahhing and diggin' it. The moon is cool on cool.


Posted on sf-bay-tac Wed Jan 28 22:13:21 2004 PT
Converted by report.pm 1.0 Thu Jan 29 20:54:22 2004 PT