Eyepiece wobble

[UKDiver]

While using Celeston plossls with a Takahashi 1.25" prism, I had wobbly eyepieces when the eyepiece holder was tight. What have I got wrong? Is this a function of undercuts or is this normal?

Adrian

 

[Pixies]

The Tak prism has a twist-grip doesn't it?

The eyepiece undercuts are designed to work with thumbscrews but can cause problems with compression rings. It might be that the Tak compression ring is unable to get a proper grip with the Celestron undercuts.

[mikeDnight]

Some undercuts are deeper than others. It's a shame there isn't a standard depth followed by all, or that manufacturers would quit with their gimmicks and return to superior smooth barrels. The Tak prism is a beaut, and it might be worth unscrewing the locking ring and trimming a few millimetres off the plastic ring, but not too much. That may allow the prism to grip the eyepiece. Alternatively,  you could roll a rubber O ring over the barrel until it butts firmly against the eyepiece  body, which should allow the locking ring to contact the 1.25" surface of the barrel. Another way to overcome the problem caused by undercuts is to use par focal rings to the eyepiece barrel. 

[UKDiver]

1 hour ago, Pixies said:

The Tak prism has a twist-grip doesn't it?

The eyepiece undercuts are designed to work with thumbscrews but can cause problems with compression rings. It might be that the Tak compression ring is unable to get a proper grip with the Celestron undercuts.

Yes, twist grip.

1 hour ago, mikeDnight said:

Some undercuts are deeper than others. It's a shame there isn't a standard depth followed by all, or that manufacturers would quit with their gimmicks and return to superior smooth barrels. The Tak prism is a beaut, and it might be worth unscrewing the locking ring and trimming a few millimetres off the plastic ring, but not too much. That may allow the prism to grip the eyepiece. Alternatively,  you could roll a rubber O ring over the barrel until it butts firmly against the eyepiece  body, which should allow the locking ring to contact the 1.25" surface of the barrel. Another way to overcome the problem caused by undercuts is to use par focal rings to the eyepiece barrel. 

Not sure I fancy cutting anything at the moment! O rings I can probably do, I suspect I must have some from old scuba regulator seals., might be too small. One for the morning. Par focal rings? More jargon to lookup.

Cheers Mike.

Adrian

[Franklin]

Just don't drop the eyepiece right in. Hold it back a bit so the diagonal tightens up around the end of the eyepiece nosepiece.