On the evening of 1 Nov. 99 while looking at the 'straight wall' on the terminator I noted that the crater Birt was casting a shadow across the wall. This came as a surprise as Birt typically appears to have no elevation at its rim. Further the shadow was broken in one region indicating a small gap in the crater rim apparently in the region where Birt A bulges into the larger crater (Rukl 54. I captured a video image of the shadow and have posted it at http://www.fortunecity.com/victorian/canterbury/222/rupesrecta.htm. Has anyone else ever noticed Birt casting a shadow across the wall? Very cool.
..............I just looked at the large scale drawing of Rupes Recta in Rukl's (image 27) and indeed he does show that Birt's rim does have elevation, and more interesting he shows a small crater in the rim region between Birt and Birt A. Well, that explains the gap.