Visible crew/equipment: When Rimmer is being questioned by The Inquisitor, a full boom mic and arm can be seen rising out of shot by the three candles on the right of the screen. (00:08:35)
Visible crew/equipment: A boom mic shadow appears on Lister's head just after he opens the door with the severed hand. (00:19:20)
Visible crew/equipment: After Lister is attacked by low Kryten, he sneaks through the cargo bay. There is a shot where the camera is following Lister as he sneaks around a corner, if you look at the floor you can see the shadow of the cameraman. (00:14:45)
Visible crew/equipment: When Binks arrives on Starbug, a boom mic can be seen at the top of the screen. (00:07:45)
Quarantine - S5-E4
Visible crew/equipment: When Lister wipes down the biohazard cabinet, a boom mic can be seen in the top right of the screen. Also, just before the camera moves past the pillar, the entire microphone and arm can be glimpsed. (00:05:00)
Quarantine - S5-E4
Visible crew/equipment: When the Cat tries to attack Rimmer in Quarantine, a boom mic can be seen at the top of the screen. (00:16:45)
Terrorform - S5-E3
Visible crew/equipment: A boom mic shadow can be seen along the bottom of the screen when the crew have to leave Starbug and walk. (00:11:25)
Terrorform - S5-E3
Visible crew/equipment: When Lister, Cat and Kryten leave the cockpit with the plan to make Rimmer feel good about himself to escape, a boom mic can be seen in the top left corner of the screen. (00:22:45)
Visible crew/equipment: At the start of the episode, when Lister and Kryten talk about Lister's comic, a boom mic shadow can be seen on Kryten's head. (00:02:10)
Visible crew/equipment: Just before Red Dwarf explodes, there is a shot of Lister. In the background you can see a moving shadow of a crew member on the floor. (00:04:25)
Visible crew/equipment: When the High Rimmer and Cat dance, in the wide shot a boom mic can be seen at the top of the screen. (00:11:35)
Visible crew/equipment: When Lister is being taken over by The Inquisitor, a boom mic shadow can be seen moving on Kryten's chest. (00:04:15)
Visible crew/equipment: When we first see the crew looking at the radar before the lights go out, a boom mic can be seen in the top left corner of the screen. (00:05:35)
Quarantine - S5-E4
Visible crew/equipment: When Rimmer asks the crew if they had forgotten Red Dwarf could only sustain one hologram, it shows a shot of the rest of the crew who say nothing. At the top of the screen, a boom mic can be seen. (00:03:00)
Terrorform - S5-E3
Visible crew/equipment: When Lister and the Cat type into the computer, in the shots of their reflections, the lens of the camera can be seen reflected between them. (00:05:00)
Visible crew/equipment: When the crew leave the Red Dwarf game area, a boom mic is visible in the top right hand corner. (00:11:35)
Visible crew/equipment: When the Cat shoots the locker which the low Lister is hiding at The End of the episode, a boom mic can be seen above the Cat. (00:25:40)
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