by Ron Bhanukitsiri
Last night the seeing is quite steady. So I decided to try for the Alpine Valley Rille (more on this later). Taking the cues from David Knisely's Saturn occulation observation, the TV-102 Light Cup searched for the Hadley Rille for the first time ever. There's a very good article about this rille in S&T July 2001 with a very nice CCD image by Maurizio's 10" Newt. I spent a total of over an hour.
Incredibly, the TV-102 found it **effortlessly** at 220x (the 4mm TV Radian was in the diagnoal while I was looking for the Alpine Valley Rille). So I kept dropping the magnification, 176x, 146x, 110x and 73x (all TV Radian). The rille could be see, smaller and smaller until it looked almost like a hair-line thin curve at 110x. 73x proved to little magnification ;-). Back to 176x for a very nice view. Up to 293x for a nice view as well, but best view at 220x. The rille curve around from one edge of the mountain around a crater to another edge. It has depth and clear width and looked like a nice little canal that use to carry water the lunar lander. The protruding ridge was where Apollo 15 landed nearby (didn't see any flag ;-). I could see the small rille next to the landing site extending from the mountain ridge: glimpse at 176x, seen clearly at 220x and 293x.
The article in S&T stated that the Hadley Rille is a little over 1km wide "but can be made out in a 5-inch telescope". Umm, an email to the editor is in order ;-). What's the minimum aperture and telescope you guys have seen the rille with?
Alas, the Alpine Valley Rille is truly a nemesis and still out of reach of the TV-102 Light Cup ;-). A rematched has been scheduled ;-).