Collimating refractors.

[cotterless45]

This Cheshire is good, just to have a check if your cell is fixed, neat,

Nick.

http://spacealberta.com/equipment/refractor/collimate.htm

[LukeSkywatcher]

I was under the impression that refracs rarely if ever need collimating. I have a 90mm refrac and i have never once given a thought to collimating it.

[Naemeth]

I was under the impression they almost never needed collimating because everything in the OTA is stable and relatively fixed, collimating is more difficult and thus the OTA going out of collimation takes a lot more. You'd probably need to drop the OTA to have it go out of collimation.

[valleyman]

Never thought Refactors need collimating

[ollypenrice]

All being well refractors won't need collimating but all sorts of things can go wrong. Collimating the individual lenses of an element with respect to each other is a job for the professionals. However, aiming an entire front element accurately down the axis of the OTA is something you can do and it is very like collimating a reflector. I did collimate a TeleVue front element years ago and just moved the front cell by hand until I got a nice set of diffraction circles in the EP. I used an artificial star in a long, dark warehouse. All this was recommended by TV over the phone.

Olly

[John]

I've owned quite a few refractors and around half of them did need collimation adjustment. Notably it was the lower cost ones that needed adjustment, I presume because of lower manufacturing tolerances.

The link provided by cotterless45 is a good one on the process. As well as adjusting the tilt of the objective lens, prior to that it's important to check that the focuser is aligned with the optical axis of the scope - if it's out then the adjustments need to be made before adjusting the tilt of the objective.

Slow refractors are relatively tolerant of some mis-collimation but it's nice to get it as accurate as possible I feel.

[LeeB]

Just about to coli my carton after great views last night , its only a bit out , but the cheshire shows slights mis. The laser shows the focuser is dead on though so should'nt be to tough. detail last night on jupiter (4-5am) was good with belts showing waves,but so bright got a slight haze cast. Disappeared on stars even bright ones and funny enough did'nt see it on the moon! or venus! it could be me going mad of course.