Wandering Down The Terminator
By David North

Tonight I decided to take the terminator in Rukl order, so I'll just arrange my comments the same way. This could get long, for which I apologize, but I had both time and inclination, if not particularly good seeing.

Rukl Page 5

Meton (along with it's subordinates) makes a weird shape of ruined walled plains that appear to be filled with mare material or some other detritus. The floors are smooth, with only one normal-looking (and small) crater inside. The smoothness was the perfect palette for the curious albedo feature I noted, however: Meton has a "dark ray" inside it, heading roughly westward, with a slight northerly trend. The angle of the "ray" did not correspond to other shadows nearby, so I'm pretty sure it's an albedo feature, but it was nearly as dark as some of the shadows.

Just north of Aristotles, a combination of rises and craters -- notably A & B -- formed an almost perfect "S" shape. The Lunar Snake! Glances at maps are inconclusive as to whether they are hills or domes; their location makes either fairly likely: they could be ejecta blobs, domes formed from the stresses of impact... beats me. Striking "asterism," though.

Rukl Page 13

At 37Nx17E on the northern shore of Serenitatis there is something of a standout mountain I've not noticed before, named Alexander Kappa (if I read the tiny letter in the Times Atlas correctly). It casts a shadow all out of proportion with nearby peaks, including the isolated clutch just south of it. I say "it" somewhat inaccurately; there are two peaks on the mountain, but it's only given a single designation.

It's a curious sight, and no explanation for this solitary giant comes to mind.

Rukl Page 23

Overall, the light was simply inconstant tonight. Linne was in some evidence, but not as bright as one might expect. Paradoxically, Sulpicius Gallus was "puckered" and obvious. Odd when Linne is dim, Menelaus was very bright, with startling reflections off its westward rim. I can only guess this is an effect of the low sun angle hitting ideally to maximize the reflection. Rukl Page 24 Bessel is basically grand central station, and in the right light this effect becomes striking. Three branches of dorsa converge on it, but none of them are particularly notable (I'm unclear of their names; they seem to be extensions of Dorsa Lister in the southeast, Dorsa Buckland to the west, and Dorsum Azara to the north. But none of the branches of which Bessel is the hub are designated specifically.

The light was so oblique that the north/south portions seemed almost like rilles, but they could be distinguished as dorsa fairly easily because they were (a) quite wide and obvious, and (b) I'm convinced if there were a rille that choice I'd know it by now!

Rukl Page 34

There is a particularly pronounced gouge running from the north side of Julius Caesar directly to Sosigenes. At the northwestern end, it seems to branch into a "Y" shape with some particularly steep scarps abutting the eastern edge, and something that appears like a rille without being convincing. This turned out to be an interesting observation in that the Air Force charts have a similar ambiguity in the same place; the artist marks a vague line, unnamed, in a light tone. I don't know what to make of it, but it was fun to trace.

Rukl Page 45

As I am currently slogging my way through all kinds of odd Cartesian geometries, and he was an enigmatic personality, it's only fitting that Descartes was the most interesting thing to see in this area. It's an old crater, somewhat ruined, but some of its curious history can still be read. Concentric with its battered walls (almost gone in the north) is a distinct rille-like ring. Rather than assuming two hits in the same place, this looks like a slumping fault, a sort of miniature of the effect we see in the huge rilles around the Maria, such as Humorum or Serentitatis. Or perhaps more accurately, the same effect that is so stunning in the larger Poseidonius.

Rukl Page 56

For the nth time, I rediscover Catena Abulfeda. The crater of the same name is of little interest -- well formed with a smooth floor -- but there is a very large "ray"structure leading off to the east, with a bit of a southerly slope. Unlike more defined catanae, it also seems to incorporate a slump valley, and at times looks more like a rille than a crater chain. In this regard it reminds me of the more prominent Vallis Rheita. I guess this is just one of those nights when everything I find looks like a smaller version of another old friend.

I can't travel this part of the moon without a stop at Sacrobosco, if for no other reason than the name is so dang silly (Holy Chocolate Milk, Batman!) The crater cooperates with the joke by looking silly, too. It has three major impacts inside its somewhat indistinct walls, making it look like a happy face with puckered lips. In a more serious vein, there were some interesting albedo contrasts inside, which may just be a trick of the light, or may imply some bright ejecta from one or more of the newer, internal impacts.

Rukl Page 66

Maurolycus was only about two-thirds lit tonight, but that turns out to be a good way to see it. The low sun angle exaggerated the definition of the "messy area" in the northwest floor, which appears to be a circular slump, but not clearly an impact. It makes me wonder if the actual impactor that formed this massive plain hit off-center, or if Maurolycus was formed over an earlier, deep impact that created the weakness leading to such a slump. I have no idea. But it makes for a good "look." Adjacent Barocius also has a similar feature, but more distinct -- it probably was a later impact. But from the look of it, not much later than the major hit. Possibly even a one-two punch.

A bit north, Gemma Frisius was also putting on a good show, but considerably less well lit. This afforded a fleeting glance at its curious "squarish" internal craters. There are two similar features, one north and one south. The northern one looks almost perfectly square, with a single distended corner. The southern one looks more like a trapezoid, and a smaller crater next to it also has a curious angular appearance. I have seen this effect before, particularly the crater South near Mare Frigoris, but it usually can be traced to nearby older impacts that deform the walls in this way. But these craters show no such obvious mechanism, and I have no idea why three such are so proximal.

Rukl Page 74

At last, we come to Baco: the inventor of Baco Bits. Well, no, really it's Roger Bacon, famous Frier. Er, Friar. Anyway, the crater gives the impression of being distended on the western side, and convinces me this is a fair example of a somewhat oblique hit. The rumpling toward the west, along with the thicker ejecta blanket (almost nonexistent to the east) is fairly convincing. I decided to try to hunt for some secondary craters, but the south is such a mess that I had little luck. Also, this is probably a moderately old crater, so much of the "evidence" may be rubble by now.

Mutus and Manzinus (too bad the latter isn't "Jeffus" instead) make an interesting pair, both with flattish floors, similar tone, and not too different in size. Mutus is a bit smaller, and probably a bit newer, and has three distinct internal impacts making it a very interesting and intricate crater. Some small detail can still be seen in the wall terraces, and a curious cut runs through the northern wall. Manzinus, on the other hand, is more "blended." It also had internal craters, but they seem muted and vague by comparison. It also shows some small detail in its walls, but with less clarity. It's as if two craters were placed side by side to show the effects of age, as a study in lunar processes. Of course, the trio of Theophilus, Catherina and Cyrillus span a larger time frame, but these two can teach us quite a bit through their similarity as well as their contrasts.

Tech stuff: 8-inch SCT at 300x, 225x, 175x and 125x. General views through a 4.5-inch newt at 36x. San Jose, CA 6/30/98