L 36: Grimaldi Basin

At first glance nr 36 on the Lunar 100 list — the Grimaldi Basin — seems to be an easy catch. Its quite big and easy to spot in the lunar landscape. It is even just about visible naked eye. But the basin as such is not enough to tick off L 36 — you need to trace both its “outer and inner rings”, and that is a more demanding task.

Preparing for my observation I consulted a number of maps and images to make sure that I had a pretty good idea of where to look for traces of the rings. Still, and at the telescope, the outer ring was far from obvious. Some parts stood out alright, especially on the eastern side, others were more difficult.

Covering such a large area it took me almost an hour to complete the sketch. Even so some parts were sketched rather haphazardly, and especially the southern parts could have used more attention.

Observed 26 October 2015, UT 19:00, using a SkyWatcher 10″ and a TeleVue Nagler 3-6 zoom eyepiece. Seeing 2-4/5. South is up.