Hitchhiker's Guide to Rukl Chart 4

Alpine Valley

Alpine Valley Rille (JRF <freeman _at_ netcom.com>)

The Alpine Valley, or Vallis Alpes, is a strikingly straight and relatively narrow gash through the eastern Alps. A narrow rille runs along the center of the floor, and is an interesting challenge for small to medium apertures. Its visibility is best at low sun angles. I have seen the entire length in an 8-inch Newtonian at 254x, but on the same occasion could see no trace of it in a 90 mm fluorite refractor at 202x. Thierry Legault's CCD image of Plato (bottom right), the Alps (top left) and Mons Piton (top right) at the edge of Mare Imbrium.

Alpine Valley (David North <d _at_ timocharis.com>)

The "Gash Theory" Of The Alpine Valley Formation

The first hole in the 'gash' theory came when larger apertures were able to image the "river" in the valley. (there is a "riverbed" that runs all the way through). It was kinda hard to figure out how a gash could cause that.

Current ideas involve actual water movement when there may still have been some (highly questionable) and more popularly the idea that it was some kind of lava tube (or flow) between the maria. This is supported by the small "collapse craterlets" that formed along the "riverbed" or interior valley.

By the way, I've peeked the "river" with the eight inch, and got a pretty good look at parts of it with the twelve; I really don't know what the minimal aperture might be to see it.

Still, the way it cuts through the Alps is simply amazing. I'm not sure there's a similar valley anywhere on earth, though to me it seems more consistent with rift geology.

It's my understanding that it's a real bear to image, which makes sense to me as I find it a real bear to see... but I noted some time back that it looks like Thierry Legault nailed the easiest part of it (in the "pond" nearest Mare Imbrium) with his 225mm SCT.

The rille is "collateral damage" in that Plato was apparently the target (for extra credit, count the craterlets and check out the clean split on the fine "double crater."

Those Tak SCTs are amazing! Well, so is Theirry...

There is also a curious eastish to westish line starting beyond Rima Archytus (that includes it) running along the northern edge of the Alpine talus that breaks suddenly at the end of the valley, subsequently trending more southerly. There is a tentative hint of this in Rukl's drawing, and equally vague but notable indications of same in the Times atlas. I suspect this to be a large but obscured feature related to Imbrium in some fashion.

Alpine Valley (...Akkana)

I have seen part of the Alpine Valley in a 6" f/8 reflector. David Knisely commented on sci.astro.amateur that the best time to see it is at greatest northern libration, and when the valley is close to the terminator.

Bratislav <epabcc _at_ broady.ericsson.se> commented on sci.astro.amateur:

> Good indication of seeing are craterlets
> at the floor of nearby Plato. If you don't see at least 4 or 5, don't
> bother with the Rille.

Wrinkle Ridges near Valles Alpes (David North <d _at_ timocharis.com>)

I noted a curious "line" running almost directly north from near the base (Imbrium side) of Vallis Alpes toward Mare Frigoris. There is nothing charted there, or named, to my knowledge, but it certainly looks like a rille structure to me. In Rukl there is some indication of a curious linear crater formation, but no comment or connection. In the Times Atlas, based on the Air Force charts, there is clearly an indication of such a structure, but no named confirmation. Anybody know if this rille has been positively identified and/or named?

Barrow Ray (Larry B Smith <KTBNDRY _at_ paonline.com>)

August 14, 2002: I noticed a sunrise ray at Crater Barrow. The ray originated from the east wall at approximately 71.5 N lat and 12.5 deg long. The ray projected 75 km across Barrow's floor and ended at the western sunlit rim of the crater and just to the north of Barrow A. Viewing in this area is difficult due to crater's relatively close proximity to the lunar limb and the nearby terminator.

Sketch of the Barrow Ray by Akkana Peck, October 12 2002.

Wrinkle Ridges in Mare Frigoris (Robin Casady)

Mare Frigoris showed a very distinct, but short, wrinkle ridge half way between Plato and Timaeus. Rukl's chart 4 shows an unnamed ridge in about the right position. However, what we saw seemed to be at a slightly different angle. We also saw a parallel ridge that was not as distinct, but it seemed closer to the first ridge than Rukl indicates.

Timaeus/Archytas Wrinkle Ridges (David North <d _at_ timocharis.com>)

A small clumping of tiny marks one the edge of resolution along a wrinkle ridge just south of Timaeus and west of Archytas hints at significance, and there is a vague indication of a small crater group there in all my charts.

Anaxagoras (Akkana)

The most prominent crater near the north pole at full moon, Anaxagoras shows a nice system of rays.

De La Rue (Steve Coe <scoeandlross _at_ sprintmail.com>)

There is a central peak, but also a central crater. Both features are side-by-side in the middle of this crater. The floor of De La Rue is quite hummocky (sp?), there are lots of small craterlets and little mounds break up the floor, so that it is not flat and certainly not smooth.

De La Rue (...Akkana)

Big central crater, with small auxiliarry craters to the west and southwest. West-Southwest of the central crater is a feature which looks like a mound rather than a crater; Rukl's sketch isn't clear on what it is.