Originally Posted by Musoman
Cheers Paul - as you say , its the right piece but the retaining ring has disappeared, so i have used some seriousy strong marine 2 pack epoxy, and simply glued the lens in to the housing
Just need to find something to hold the whole thing in the extension tube.
Try using foam material of some kind. I've used foam tape and foam material from an old exercise mat. Use as many layers as required cut at the right length to fit perfectly arount the TN, compress it to fit the foam/TN assembly inside the extender and let it expand. It will prevent movement and will center the TN perfectly inside the extender. Black foam will also flock the inside - if it is shiny, make it mat with sandpaper.