At a low sun angle (and during good seeing), a five or six inch should show all three (Armstrong, Collins, Aldrin). The smallest is probably Collins at 2.4 km (1.5 miles) in diameter and is a little over 19 km from the landing site, with Aldrin at about 3.4 km (2.1 miles) in diameter (47 km to the northwest of the landing site), and Armstrong at 4.6 km (2.9 miles) in width, 49 km northeast of the landing site. "Cat's Paw" is the closest crater to the Apollo 11 landing site that is visible in amateur scopes, and is a bit on the irregular side (3.7 km x 2.4 km), but an 8 inch should just catch it as well. As long as the seeing is good and the sun isn't too high on it, I usually don't have a lot of trouble with Cat's Paw in my 9.25 inch SCT, although it isn't exactly a prominent feature. Cat's Paw's east rim crest is about 5.5 km (3.4 miles) from Apollo 11's landing site location, and the tops of the Cat's Paw crater's ramparts are visible in the horizon shots taken from inside Eagle shortly after landing (see image below (courtesy NASA)):
Edited by David Knisely, 23 July 2019 - 07:43 PM.