collimating and movement in the eyepiece

[proflight2000]

I appreciate this might be an odd question, but when any of you collimate using whatever method apart from a cap, how do you compensate for slight movement with the 1.25 or 2" fitting. I have noticed that I can collimate and its ok, however due to a very slight slackness in the eyepiece holder there can be some up/down or left/right movement. Any tips.

[nitram100]

Yeh, this annoys me aswell, my cheshire wobbles all over the place, so i just rotate the OTA in the cradles until the focuser is pointing towards the ceiling and leave it like that, i don't tighten it or anything.

[SteelRat]

Could try building up the thickness of the collimator with a layer of insulating tape? Maybe? :?

[Andrew*]

I think you should tighten the collimator. Afterall, that's what you do with eyepieces...

Andrew

[proflight2000]

I used tape to tighten the fit, the problem here is that it does not ensure a square fit in relation to the dot on the mirror, for example, the other day i did a collimation, then I did a laser collimation, in text book terms that should have been ample, however when I bought the scope back indoors i tested the collimation sing the chesire and it had moved at least 7mm from where it had been previously. I appreciate that temprature etc can play games with the mirror, then I cottoned on that the collimator was not sited exactly as I had sited it previously.

The difference is not remarkable, but something i didnt take in when the original collimation was done. I have now decided to put the collimator in an old barlow tube to see what difference that makes.

[nitram100]

I've read that alot of people tighten the collimator like they would an eyepiece and tilt the ota to the position it would be in a typical observing session.

[lunator]

I tend to collimate with the scope in a near horizontal position. I tighten the retaining screws as I would for an eyepiece. Any system using retaining screws will not be perfect.

There is always the issue of the tool not being optically centred but if you take care then it should be close enough. For absolute spot on collimation you need to do a star test on a steady night.

Cheers

ian

[FLO]

Probably worth mentioning, when selecting accessories like focus extenders, 2"-1.25" adapters and focusers, look for the compression-ring style fitting (popularised by TeleVue) which does a better job of holding/centring the eyepiece.

[blinky]

Could try building up the thickness of the collimator with a layer of insulating tape? Maybe? :?

Exactly what I did with one of my EP's that was a bit loose.

[The Warthog]

I've read that alot of people tighten the collimator like they would an eyepiece and tilt the ota to the position it would be in a typical observing session.

Thisis what I do. If the collimator were very loose, I suppose I could shim it with thin card stock.