by David North
Sometimes the night can make the choice of scopes a real quandary.
It was cloudy all day and I hadn’t been planning to set up anything beyond maybe the 4.5 newt, but it broke somewhat clear near sunset. I didn’t expect good seeing, and a developing fog was promised, so at the last moment I decided to set up the five inch refractor rather than the C8, on the assumption that it would work better in weaker seeing and be less likely to dew up.
Just to mess with me, at sunset the seeing was magnificent. Made me wonder if the decision had been wrong and more aperture was in order... but not long after that a haze set in and things got moist, so I lucked out and (maybe?) guessed right after all.
The window of really good seeing was short -- only about 45 minutes -- but sweet.
Other than a general survey, I only looked at two areas closely: Triesnecker and Sulspicius Gallus.
The Rimae Triesnecker (Rukl 33) were magnificent. The main branches run north and south, and on a typical evening will seem to extend maybe half way to the end of Rima Hyginus (Rukl 34) in the north and near Rhaeticus A in the south. There are some minor crossings near the center that make it look crosshatched.
Tonight however, all the filigrees could be seen, running almost to the tip of Hyginus rille, and all the way down and by the main crater Rhaeticus. I counted 18 separate threads of varying width in all, building to a construction that was simply sublime. If you ever get a clean shot at Triesnecker rilles right on the terminator like this, I suppose you might forgive yourself for using so much of the time available on them.
The basic form of Rima Hyginus was quite clear, but even during this "show" put on by Triesnecker, the craterlets inside the rille were somewhat difficult to pick out. This you may list as example #2,943 of Dave's Curious Things That Just Don't Seem Right When Looking At The Moon, But There You Are. Usually the craterlets are easier than the fine sections of rille nearby, but not tonight.
Sulpicius Gallus (Rukl 23) is itself a somewhat ordinary medium size crater. Just to the north and west is a smallish but striking rille complex of the same name, easily seen tonight as a fat main rille with a short subtle parallel secondary.
More interesting, possibly, was Sulspicius Gallus A, a small but perfectly formed crater near the northwest end of the rille. It was in "full pucker" (when the low light is such that the rim is well outlined) but the bright ejecta blanket around it was very pronounced. The effect with the glistening rim, dark interior and white ring around it was very much like an eyeball staring back at me.
As folks used to say in Welles books, "Hullo..."
David North
128mm refractor at 200x