Mons Rumker is a lunar dome way out towards the moon’s limb, making it challenging to image from the window-sill.
Sky and Telescope, in https://www.skyandtelescope.com/observing/a-little-guide-to-lunar-domes/ says
“Mons Rümker forms a large, pudding-like mound of some 30 domes piled one atop the other in far western Oceanus Procellarum. The feature appears quite foreshortened near the limb – – – – – – The mound is about 43 miles (70 km) across and climbs to 3,608 feet (1,100 m) above the plains. Rümker represents multiple, massive outflows of lava. Amazing!”
I have been waiting ages for the correct lighting conditions, and tonight was the night!