Coincidentally, on Sunday night I was looking at a lunar crater that was named after Nasmyth. When I first looked near the terminator around 9 pm I was surprised to see what looked like a large crater cut in two by illumination. Half of the crater looked jet black, half looked fully illuminated, despite the fact that both halves were on the bright side of the terminator. (The line between dark and light ran perpendicular to the terminator, not along it, so this was not the usual sunrise phenomenon). Instead, it suggested that the walls of the crater were higher on one side than the other, allowing light through to only half the crater.
Over the next couple of hours, this dark half began to be illuminated as well, and I could see that what originally looked like a single crater really was two different large craters, Nasmyth and Phocylides. Nasmyth is older and has a lower crater rim (the bright half in my earlier view). Phocylides is younger, overlaps Nasmyth, and has a higher crater rim. This produced a striking dark half withing what looked liked a single crater in my ealier view. The interior wall separating the two craters (the border of Phocylides) was not apparent at all when I first looked but began to pick up light as the night went on.
I didn't know who Nasmyth was until looking up the Dob history the following night. Nice connections here between eyepiece experiences and discussions on TAC.