by Marek Cichanski
Moon from home 6" Mak-Cass (Intes-Micro Alter M603) CG-5 mount Eyepieces: Tele Vue Naglers, mostly 16mm T5 and 7mm, 5mm T6
Seeing was pretty decent, around 3-3.5/5.
Craters Aristillus and Autolycus were right on the terminator. The eastern slopes of the Appenines were catching the morning sun. Portions of some of the peaks resembled snow-clad mountains on earth.
The Alpine Valley was just catching the light, with the same 'ideal' illumination that Rima Ariadeus had last night -- the S-facing edge of the N rim was brightly lit, but the interior was in shadow. Rimae Triesnecker were also looking really nice.
Good gawd, but I was tired... several nights in a row of observing took their toll. Almost nodding off at the eyepiece...
Now that Charles Wood has published his "Lunar 100" list, I can apply "search and destroy" observing to the moon. I've observed about 60 or 70 of the objects by my rough count, based purely on memory, without looking back through my notes. Now it's on to the higher-numbered, more challenging objects. I decided to search for L99, because it was near the terminator tonight. The description in the S&T article calls it the "Ina Caldera", saying it's a "D-shaped young volcanic caldera". Whoa! An actual endogenic explosive volcanic feature? And young? This sounds exotic. I tracked down a reference to it on the net, and sure enough, researchers who've studied it think that it might be related to fairly young outgassing or other volcanic activity. Well I'll be dipped...
So, I tried to see it, and mostly got my butt kicked. It's in Lacus Felicitatis, somewhere to the SE of the crater Conon A, but I didn't quite have the seeing and/or lighting to spot this 3-km-wide feature. I might have seen a tiny whitish dot in L. Felic., but I can't confirm that it was Ina. Looks like it's number 99 for a reason. It's good to have some hard, elusive targets - it makes it that much more satisfying when one finds them.
The crater W. Bond (L76) was interesting. Wood describes it as a "large crater degraded by Imbrium ejecta". It looked to me like it had what I call "pebbly ejecta" in it. This appears to be Imbrium ejecta. The walls are low and irregular. It seemed reasonable to me to call this crater pre-Imbrian, and to suppose that its rims had been battered by, and its interior partially filled by, Imbrium ejecta.
Way too tired at this point, had to go inside and get some shuteye...
Good seeing, 3-4/5.
At 19:30 PDT, the tip of the central peak of Moretus was just getting lit. The classic "point of light in darkness" effect.
Rupes Recta was just in view, casting a nice shadow. The floor of Plato was completely in shadow, but the W rim was lit.
I wonder if this plateau-forming material around Ptolemaeus is the Fra Mauro formation? Lunar geologists have always made a big deal about the FMF. As far as I know (which isn't very far), it's Imbrium ejecta. Because the Imbrium impact is such an important event in the relative dating of lunar features, the date of the impact represented an important point in the timeline. Apollo 13 was supposed to land on it, but that didn't work out, and when Apollo 14 did land there, the samples they returned didn't seem to provide the high-precision dates that everyone had hoped for.
The floor of Ptolemaeus has a number of depressions. Rukl's drawing makes
them look like buried craters. Lessee, what can I see in Ptolemaeus
tonight?...
Ammonius (=Ptol. A)
Ptol. B (L75)
Ptol. D
Ptol. M and the depression that it's on the NW edge of.
Thinking about craters that are buried, but still visible... I wonder how in the world the lava can bury these craters without totally concealing them? Why in the world would lava "drape" over a structure like a pie crust drapes over the apple chunks? That doesn't fit with what we know about runny basaltic lava. It ought to lap up against the edges of the craters. Could it have something to do with the cooling of lava when it thinly overlies a bedrock obstacle? Are there terrestrial examples of things like this? I have a lot to learn about lunar geology...
Gylden Valley (L92): Ooh, an L target in the 90s to go for... Is this just the big valley along the SW side of Gylden? That didn't seem so hard. It's easy to see that this is probably part of the Imbrium sculpture, given its orientation. There are other 'sculpture' features here, both ridges and clefts.
When the Imbrium Sculpture is near the terminator, it's one of my favorite lunar features to look at. What a graphic, dramatic illustration of the power of a basin-forming impact. Just thinking of all that debris blasting out from the site of the impact, scouring great furrows in the surrounding terrain with flying, mountain-sized tools. Wow...
Later: seeing dropped to around 2.5-3 /5.
Could still make out the Regiomontanus central peak, with its crater Reg. A (L46). Is this a summit crater in a volcano? If you ask me, it's a coincidence. I think a bolide hit the mountain.
Mosting A (L61): Nice simple crater, clearly the youngest thing in its immediate vicinity. Little or no obvious ejecta.
Catena Davy (L51): Didn't look great in this seeing, but was visible. Could distinguish individual craterlets. Could believe that it's due to a "fragmented impactor".
Seeing was pretty cruddy, 2-2.5 / 5.
Dark patches in Alphonsus were nice albedo features (L47).
Copernicus was dramatically lit: Floor and central peak in shadow, but inner W rim was fully lit, and the terracing showed nicely.
Rima Hadley (L66): Saw the elongated "Bela" crater, and maybe I got fleeting glimpses of rille between Bela and Santos-Dumont C, but couldn't see it between S-D C and Mt. Hadley Delta.
Could just see Rima Birt.
Apollo 14 site was nicely visible. (L67). Interesting that they didn't land on the big plateau on the NE side of Fra Mauro, but rather on the smaller hump at the N edge of Fra Mauro X.
The seeing eventually got too soft and wonky, and I went inside to watch the World Poker Tour...
Seeing about 3/5. Better than last night, but still a bit watery.
Copernicus H (L74): Cool! There it is! (7mm Nagler) Very distinct dark halo in this illumination. Halo stood out well against the light background of Copernius ray material.
Copernicus looked great. The terracing on both the E and W inner rims was very distinct. The "diving board" promontory on the E rim was also very distinctive. Terracing was also nicely seen in Tycho.
The little "islands" that (presumably) give Mare Insularum its name were really neat in this light. They're interesting to think about -- are they Copernicus ejecta? I doubt it -- too big, too far from Copernicus. Plus, this would make Copernicus a pre-lava crater, which I doubt. (But, it does have a flat, lava-like floor. Is this impact melt? Mare lava?) I'm guessing that the "islands" are Imbrium ejecta. (I wonder if they count as part of the Fra Mauro Formation?) The floor of Copernicus looks lower than the level of the Imbrian/Procellarian lavas, so I'm guessing that the floor is impact melt.
The Copernicus area is a neat place to do this sort of geologic work. It's no wonder that Gene Shoemaker used the Copernicus area as his first detailed study in lunar geologic history. Like everything else in lunar geologic studies, this is nicely summed up in Don Wilhelms' excellent book "To a Rocky Moon". I'm going to take the risk of quoting a good-sized passage here...hope I'm not getting in any copyright trouble... This is from a section called 'Shoemaker's Creative Burst (1959-1960)' :
"...Shoemaker was already studying the Copernicus region intensively with a superb photograph (purchased at the Caltech bookstore) that Francis Pease had taken with the 100-inch Mount Wilson reflector on 15 September 1919. Thus he had the makings of a geologic map; he also had already thought of what he would show on such a map if he were to make one. Now was the time. He went back to Menlo Park, had a copy of the LAC base made, set to work, and a week later had completed the second modern lunar geologic map. There were map units for parts of craters, the maria, the mare domes, and a regional terra-blanketing unit, all of which were arranged in order of age into five named age units: the Copernican, Eratosthenian, Procellarian, Imbrian, and pre-Imbrian systems."
For me, this is the stuff of legend. What an experience that all must have been for people like Baldwin and Shoemaker! To have this plum just hanging there, neglected, waiting to be picked! And to be able to decipher it with the most basic, rock-solid principles in the geologic sciences. What an adventure.
The Hortensius and Milichius domes (L65) were showing up nicely, especially Milichius Pi and a larger dome WNW of it. The Hortensius domes were slightly less distinct, being a bit farther from the terminator.
Ooh, here's a toughie... do the domes predate or postdate the Copernicus rays? That's really hard to tell. This would probably require observations under a variety of illuminations. (I'll bet the domes are much older than Copernicus.)
Looked for the domes bewteen T. Mayer Alpha and T. Mayer Zeta. Tough! I think that these have to be right on the terminator, as noted in Rukl's sidebar on p. 86. I could see one dome on each side (NW and SE) of Zeta. The one on the NW side might have showed a bit of a summit crater, but I wasn't sure. The biggest dome in the whole area seemed to be S of Zeta and NW of Milichius.
The Rimae Hippalus looked GREAT! Great lighting. (L54)
Kies Pi was visible, but just barely. A bit far from the terminator. (L60).
The Rima Agatharchides was visible about half of the time. The seeing wasn't great at this point, but it had its moments.
The wrinkle ridges in western Humorum looked magnificent. I'm surprised that they don't have individual names.
I tried to see L69 (The Copernicus secondaries near Pytheas), but the wobbly seeing didn't give me much to work with. Could see a few of 'em, and the catena north of Stadius M.
No joy on L98 (flow fronts in Imbrium.) Sun too high.
Finished the evening by watching Io ingress on Jupiter.
Okay, here's another snippet from Wilhelms' book that I think Bay Area folks will love, especially those of you who've done the volunteer nights at Lick:
"During the UCLA grind I visited JPL and saw Ranger spacecraft being built. Knowing of my interest in such matters and my lack of interest in the oil companies that hired most geologists, another student told me about some guy who was at Caltech interviewing people who might want to work ont he Moon. Shoemaker presented an unsurpassable opportunity to combine my childhood interest in astronomy with my adult profession of geology. After later reminding him who I was with a letter that included words to the effect, 'Obviously I'm your man', I arrived at Menlo Park on Monday morning, 3 December 1962, a month and a half after the missile crisis and three days after finishing my Ph.D. dissertation. Fantasy became reality within a week as I took my first turn observing visually with the magnificent 36-inch refracting telescope at Lick Observatory. All astrogeologists were assigned a LAC quadrangle to map geologically, as well as to one or more projects that more or less matched their interests or talents... I relished this telescopic observing more than anything else I did during my career. This taste was not shared by everybody... But picture the dome's interior rimmed by soft red lights, the gentle onshore breeze from the nearby Pacific, and the night quiet except for the humming telescope drive, classical music from the radio, and only an occasional creaking noise from somewhere in the dome to remind one that the earthly remains of James Lick are entombed in the telescope's pier."
Whoo-aah!
(Apologies to Don Wilhelms for quoting so freely from his book. But it's a must-read!)
Posted on sf-bay-tac Apr 30, 2004 12:32:43 PT
Converted by report.pm 1.1 Jul 10, 2004 22:51:03 PT