Cheshire collimators

[TonyOwe73242661]

On eBay I've seen several adverts for Cheshire collimators for Newtonian ''refractor' telescopes. I've contacted the various suppliers but got no answers to my query see below:

By default Newtonians are not refractor BUT reflector telescopes.
I have an old Broadhurst Clarkson 75mm 1200 [circa] fl refractor telescope and wonder if your item can be used to collimate its single lens.
There are no mirrors on my telescope

The items listed appear to have cross wires held in by a locking nut - see attached image - but I do not know whether this locking ring can be removed and the collimator used without the cross wires to collimate a refractor telescope!

Any help/information welcome

[RT65CB-SWL]

Hi @TonyOwe73242661 and welcome to SGL. 

The locking ring can be removed as the crosshair wires are sometimes glued into grooves in the barrel.
It was on the one I had... lost it somewhere or let someone borrow it and/or they failed to return it.

Edited September 17, 2021 by Philip R

[TonyOwe73242661]

So the cross-hair wires have to be removed from the barrel before the unit can be used to collimate a refractor.

I'm surprised they are not attached to the locking ring.

Can they come away easily [from the barrel] or are they destructively removed?

regards

[Boki Aristarh]

Dear Tony,

I collimated my TAL-100R with such Cheshire.

Maybe easiest way is to read this topic: 

https://www.cloudynights.com/topic/386603-cheshire-refractor-collimation/

Happily it is so easy to collimate f/16 scope... 🙂

P.S. It is not necessary to remove wires....

[TonyOwe73242661]

3 hours ago, Boki Aristarh said:

Dear Tony,

P.S. It is not necessary to remove wires....

Does not the centre of the 'wires' interfere with refractor collimation?

I understood that the wires were for reflector scopes????

[Alan64]

10 hours ago, TonyOwe73242661 said:

Does not the centre of the 'wires' interfere with refractor collimation?

I understood that the wires were for reflector scopes????

The cross-hairs are to help to centre the secondary-mirror directly under the focusser's draw-tube...

Note the "pie slices", nice and even.  Now, my own is actually a simpler sight-tube...

I also use it for the final "home run"...

I also have a Cheshire, for refractors only...

Modern Cheshires include the the cross-hairs of a sight-tube; a combination of the two.

You can see how small the area is within that refractor's scene.  Cross-hairs are not necessary, and might make it difficult to see that small scene clearly.