I normally use my Tele Vue 13mm Nagler Type 6 eyepiece in my telescope, but I am using it here to align the Plugable Microscope by shining the light through and lining up the reflections. You don't want to know how much it cost, trust me. I got it before I got married.That looks like what I was trying to do with my "optical leveler" idea! I can't figure out what it's doing. What's it normally used for? Seeing all the cool tools you have is starting to make me think I need a bigger toy budget.
The Tele Vue 13mm Type 6.
This is a pretty interesting article about how Al Nagler helped with the Apollo Missions.