Recently I’ve been testing various 2” eyepieces in some of my 2” diagonals. Most of my diagonals either have a 'Fast Lock' type or are Baader ClickLocks.



The Fast Lock type has rods or binders inside the draw tube which engage the eyepiece barrel when the lock is twisted. As a further measure the lever itself can be threaded in as an extra safety lock.



The lighter Baader ClickLock mechanism uses a compression ring type 'collet' instead of rods and has no safety lock.



The rod binders can be seen in the Fast Lock type below:



Most 2" eyepiece barrels work in either type. However, my 19mm Celestron Luminos has never been totally secure in the Fast Lock type and required the safety lock.



Unfortunately when I recently tried the Luminos in the Baader ClickLock it became stuck fast. Luckily this was during indoor weight and balance trials and not outside in the night. I rarely used the Luminos in the Baader dielectric and it was quite disconcerting to have it inextricably stuck in the ClickLock.



Eventually I had to unthread the ClickLock mechanism from the diagonal housing and also unthread the Smyth barrel from the Luminos. No mean feat considering I am partially paralysed in my right arm and hand. The slight scoring on the Luminos barrel as a result of this activity can be seen in the above pictures. The Luminos undercut is almost certainly the culprit as I've never had any 2" eyepiece stuck in a Baader ClickLock before.