Well, I guess I'll try to combine several ORs into one, and just hit the
highlights from each of the last several nights...
Moon from home
6" Mak-Cass (Intes-Micro Alter M603)
CG-5 mount
Eyepieces: Tele Vue Naglers, mostly 16mm T5 and 7mm, 5mm T6
4/26/2004:
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...
4/27/2004:
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".
4/28/2004:
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...
4/29/2004:
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!)
Marek Cichanski
Received on Fri Apr 30 12:31:53 2004