Collimating a refractor

[Tron]

Taking of the objective lens on a refractor to clean the inside of it, is there any tools to help align the lens like collimating a reflector? Never done this, hope not to but just curious lol

[Merlin66]

Yes,

You need a laser collimator and a Cheshire eyepiece.

The laser allows you to align the focuser with the centre of the objective....

and the Cheshire allows you to see the reflections from the various lens elements so can can collimate them to the optical axis...

Note: not all refractors are fitted with collimating screws - which makes the job a bit more interesting!!

HTH

[Tron]

I can't see any screws lol I think the lens just threads in.

I see 2 small pinholes on the front lens frame... that is all, nothing on the tube just the collar.

[John]

I use a cheshire eyepiece to collimate my refractors following these guidelines:

Refractor Collimation

Some refractors have a collimatable objective lens cell, and some don't as Merlin66 says. With those that don't some degree of adjustment can be achieved by slightly tilting and shimming the focuser unit. Other tricks include loosening the lens retaining ring with the tube pointing upwards and gently slapping the objective cell sides to ensure the lens elements are seated. The retaining ring, when re-tightened, should be just tight enough to stop the lens elements rattling, ie: not too tight.