by Bill Arnett
About 1am Monday, after giving up on the rest of the day's chores, I decided to open the roof of my observatory and peek at the Moon with my 12" LX200 just to see if it was even half way decent as it will probably be the last chance for a while (given my aversion to early morning). And whadda ya know, it was really nice, better seeing than I've had in a week or more. Tonight seems to be sunset on Treisnecker et al. Pretty. Scanning north Rimae Hadley and Bradley were easy, although the big bend in Hadley where it goes into the little valley where one of the Apollos landed was invisible. But that damn rille in Valles Alpes still eluded me! And tonight seemed like the perfect shot: the libration seems to be such that Valles Alpes is much farther from the limb than usual. I tried LOTS of magnification, still no luck.
But my mirror was not cold and the Moon was only 30 degrees up. So I've come in to fiddle with the computer for a while and warm up.
Before I came in, I took a peek at Saturn which was just rising over the roof of my house. It was terrible! I was confused after the nice view of the Moon. It didn't seem to be stray light from the Moon or particularly bad seeing. Then I noticed that I was pointing so low that most of the aperture was blocked by the top of my windows. I was looking thru less than 10% of my aperture! No wonder it was so dim and fuzzy :-)
.......5am...
Well, it did get better. But I still couldn't see the damn rille. I tried a half dozen eyepiece combinations all the way up to nearly 1000x and down to 250. Once or twice I thought I might have a hint of something but it was more likely just out of focus weirdness. As one last experiment, I set up my 10f6 Dob. And BINGO! there it was clear as a bell. I switched back and forth three or four times and each time it was easy in the Newt and impossible in the SCT.
I'm jazzed to have finally seen this elusive feature! I've been looking for it for more than a year. I saw it pretty much the whole length of Valles Alpes except for the very SW end. There is also a bunch of craterlets and other stuff there including a prominent transverse feature of some sort right in the middle. My first impression of the rille was that it was a catena instead of a rille but it looked more like a rille after a while. It was pretty clear in the 10f6. But this was a very good night with perfect lighting and a good libration. I can see why this thing isn't often seen! OTOH, I wonder what it would have looked like in a big refractor?