Those Elusive Rilles!

[cloudsweeper]

Another Wow moment this morning!

6.35 - 7.15.  Moon at about 46deg, east of south, waning crescent.  10" Dob in action.  Main targets: Gassendi and Mare Humorum, close to terminator.

The Liebig Scarp (cliff) stood out as a dark gash with a craterlet at the centre, and Gassendi's details (peaks, many rilles, some pits) were clear and rewarding.  But finer features became apparent when I went from x212 to x254 (any higher, and clarity was lost).

In more stable moments, and aided by the recently-fitted focuser reduction gear, the Doppelmayer Rilles (south of Liebig) sprang into view as very delicate threads.  They could easily have been missed, except for the right combination of mag, steady conditions, and spot-on focus.  What a treat! - a thin, pale, elusive crack, branching at the northern end into what looked to me like an H pattern.

Back to Gassendi, and its rilles looked even clearer, criss-crossing its floor.  Then to the south, another rille crossed the western edge of the sea - Mersenius Rille, I believe.

What a delight it is to tease out these delicate features under the ever-changing illumination of our Moon.

Doug.

[Footnote: The reduction gear initially slipped after fitting, until I replaced the grubscrews with cone-ended versions, which engage the holes in the focuser shaft and prevent said slipping.  Takes a bit of patience to line everything up, but is a worthwhile modification.]