I've been looking for this clip for a long time, and thanks to a head's up from Jerome Wybon (of the Forgotten Silver blog), I can now share it here with the rest of you Star Kids!
I dimly recall that I saw this rare Starlog TV commercial just once, and I believe it was during the 1978 airing of the Saturn Awards show. Amazingly, the Saturn Sci-fi Movie Awards, presented by the Academy of Science Fiction, Fantasy & Horror Films, actually aired on one of our local television stations (WCSH) for two years during the height of the Space: 1970 era - in 1978 and '79. If I recall correctly, the 1978 awards were co-hosted by Mark Hamill and Caroline Munro! (The '79 show was hosted by William Shatner, and his performance of "Rocket Man" has since become legendary!)
Anyway, here's the great Robby the Robot pitching a subscription to Starlog magazine - the periodic Star Kid bible - in its late 70s prime!