A cathetometer is an instrument for measuring vertical distances in cases where a scale cannot be placed very close to the points whose distance apart is desired.
I made this cathetometer in 1983 as an apprentice work in my second year. It's now time to finish it by adding the missing part which are the tube air level and one air level as well as the telescope lenses and cross hair indicator.
So far I got the air levels and I used a cheap binocular to get a function realised, but the result is not satisfactory. I have to investigate a bit more.