Strange line on the Moon

March 10, 2008 - pm - T4S3 - 29 degrees

Now what is that!

I had been studying Mare Crisium by the light of the 3-day-old moon, having moved the 100ED to a temporary location where the trees didn't block my view. (I do like this completely manual mode of operation -simple and flexible.) Guided by a quick peek at "Jean Lacroux and Christian Legrand's fine little book, "Discover the Moon," I was focusing on small craters - and a couple of ghost craters on the western border - that are usually wiped out by high sunlight.

I found the 9mm TMB Planetary was giving me the best view - at 100X that was about the maximum the seeing conditions could justify. But as I was getting ready to clos eup shop and move to other porjects on the observing deck, I did a quick scan of the "Gang of four" craters to the south. The third one, Petavius, caught my eye immediately for its several central mountain peaks, and then I did a double take. It looked like there was a acrack running straight from one of the mountian peaks to the edge of the crater. What an unusual feature - or maybe an eyelask on the lens ;-)

It turns out it wasn't an eyelash, but one of several well-mapped rilles in Petavius. This one's nearly 50 miles long and marked on Rukl's chart simply as "Rima." I'm suprised such aprominent feature doesn't have a name. Lacroux and Legrand just give the rilles of Pa etavius a passing mention with no identification either, though they do mention the five central mountain peaks. I'll be curious to see how well these rilles hold up under higher sunlight. Maybe I caught them at just the right time, but at least the most prominent of these deserves a name.