Visible crew/equipment: When Lister and the Cat are walking through the corridor on the ship, the top of the set is visible through the transparent ceiling. (00:03:55)
Visible crew/equipment: When Lister puts his mutton vindaloo on the DNA modifier, the pole used to make the vindaloo float can be seen when the beam is cast on the dish. (00:22:55)
Visible crew/equipment: When the crew are standing before the Judgement computer (when Lister is worrying that he will be sent to prison) if you look above Lister's head you can see a microphone bob up and down into shot. (00:11:10)
Visible crew/equipment: When Ace Rimmer is talking to Mellie, a boom mic can be seen at the top of the screen. (00:04:05)
Visible crew/equipment: When Rimmer is speaking to Lister about how Ace Rimmer got all the breaks in his life, a boom mic can be seen in the top left of the screen. (00:24:15)
Answer: The cello is a large four-stringed instrument, which, when it is played, stands vertically on the floor between the player's legs (assuming they are seated). If it is to grow as large as the other instuments mentioned will, it would require a rather unseemly lack of femininity to be able to encompass it with the legs.
Rooster of Doom