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Nightspore

A Cautionary Undercut Tale

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Nightspore

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.

 

kRySNUTl.jpg

 

The Fast Lock type has rods 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.

 

3R6xA3El.jpg

 

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

 

yYLoGvMl.jpg

 

The rods can be seen in the Fast Lock type below:

 

lXsDOT5l.jpg

 

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.

 

wjQ7z8Nl.jpg

 

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.

 

NTwULl8l.jpg

 

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.

Edited by Nightspore
Don't get me started ...

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Nightspore
6 hours ago, Derbyshire Dave said:

Sounds scary. Appreciate you sharing 

I know undercuts are a problem, but this was totally unexpected. And scary lol.

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Bino-viewer

I've never had an issue with a compression ring on a smooth barrel (eyepiece or diagonal)

 

I've had lots of issues with compression rings on an undercut type design.

And as for tapered eyepiece barrels, don't even go there.....😀

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Nightspore
2 hours ago, Bino-viewer said:

I've never had an issue with a compression ring on a smooth barrel (eyepiece or diagonal)

 

I've had lots of issues with compression rings on an undercut type design.

And as for tapered eyepiece barrels, don't even go there.....😀

Slight tapers seem to be less problematical than undercuts. The 19mm Luminos stuck in the Baader dielectric was a bit of a shock. Several years ago I got a 17mm Celestron (Barsta) Plossl stuck in a Tele Vue 3x Barlow for something like half an hour. I just couldn't figure what had gone wrong. 

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