If you use a Baader Zoom for Eyepiece Projection imaging, but find the focus lengths slip due to the weight of your camera setup at some angles, then here’s a simple lock. I use 60 mm guide rings (temporarily removed from finder) connected to a small arca plate. Simply tighten the screws at the required focal length. Stops all movement and changing focal lengths is as easy as backing off the screws in one ring, rotating zoom as usual to change FL and retightening.
A super cheap alternative would be two rings cut from 65 mm PVC pipe fixed to a piece of aluminium or wood and some nylon bolts from Bunnings. Should work just as well!
