The Moon seen in the first shot of Breakaway was a 1.2m diameter model, with an electric motor that allowed it to rotate. The craters, some very large, some with rays like Tycho, are realistic but do not correspond to anything on the real Moon. It is seen frequently in early episodes.
The only use in later episodes is in library shots like this (first seen in Space Brain, and later in The Testament Of Arkadia, The Rules Of Luton and The Seance Spectre.
The special effects model at the studios and in the Space City exhibition of models (Blackpool photo by Dave Martin).
This is a Mercator map of the model, constructed by Monica Eriksson. The lighting and colour changes from episode to episode, making this a particularly difficult task. The images below show the left hemisphere (from Breakaway) and the right hemisphere, 180 degrees away (from Black Sun). The "south" lunar pole is never really seen (it's the attachment point to the drive), although some parts of the "north" lunar pole are seen in episodes such as (from War Games)
Copyright Martin Willey