The moon is about one light second away from Earth. The sun is about 600 (10 light minutes)). 52 evenly spaced planets in an Earth-like orbit would be about (

The moon is about one light second away from Earth. The sun is about 600 (10 light minutes)). 52 evenly spaced planets in an Earth-like orbit would be about (2pi600)/52 light seconds apart, which comes out to about 72 and a half light seconds. So, the closest neighbor planets would appear a lot smaller than the moon, but a lot bigger than, say, Venus. I'm not sure how widely the adjacent rings would be spaced, so you might sometimes have neighbors that are closer than 72.5 light seconds as they zip by in the opposite direction. The article also talks about arranging the planets as binary pairs, in which each planet might be very close to its neighbor, possibly appearing bigger and brighter than the moon from Earth.