Here goes a shot in the dark on a 12 year old video. Can you tell me why the pan moves it has a peg and a grove on the under side that allows it to move about a 16th of a turn? It can be set to turn to the right or to the left.
I'm a pharmacist, but had to use this video to explain to my techs how to use a triple-beam. Apparently, nobody paid attention to anything when they were in high school.