Back to basics... >_<

[EzyStyles (Eric)]

Hi guys,

What is the best and the most simplest collimator out there? currently using a laser. it points dead centre on the primary mirror and the return beam on the laser also indicates the tilt of the primary is good yet it isn't? . I knew i shouldnt have touched my collimation, now i can't reach enough in-focus with my focuser unless i take the ring out on the coma corrector.

THanks.

[rmcpb (Rob)]

The laser combined with a cheshire eyepiece to ensure the secondary is centred works really well.

Cheers

[Bill Bates]

For the secondary, a 2" sight tube 300mm long capped one end, with a 2mm central hole. The other end with crosshairs. Move the tube towards the diagonal until you see the diagonal with 2-3mm clearance all the way around as looking down tube. adjust secondary until dead centre.

A star above 70 degrees in good seeing for the primary.

[taminga16 (Greg)]

Eric, PM sent.
Greg.

[davidpretorius]

i have seen bird and paul use their cats eye collimators and to be honest, i simply want to save up and buy it.

bugga anything else

[Tannehill]

Sorry, don't follow...you can't reach focus now after adjusting your collimation? Did you move your primary mirror "down" a lot by left-turning all your primary mirror collimation bolts? I can't otherwise envision easily how collimation adjustments would affect that, unless you mean you've inadvertently decollimated so much that you have blurry images as a result.

[EzyStyles (Eric)]

Originally Posted by Tannehill

Sorry, don't follow...you can't reach focus now after adjusting your collimation? Did you move your primary mirror "down" a lot by left-turning all your primary mirror collimation bolts? I can't otherwise envision easily how collimation adjustments would affect that, unless you mean you've inadvertently decollimated so much that you have blurry images as a result.

not quite sure but i was adjusting the primary mirror collimation screw. will need to investigate into this.

I think a Cat's eye is what i need .. quite pricey though...

[h0ughy (David)]

you wont look back and it is worth the money

[Tannehill]

If you were moving your primary mirror collimation bolts, and now note that things don't seem to focus (stars don't become pinpoint, but small blurry dots?) it could be because the system is so decollimated that it mimics an out-of-focus image. The thing that threw me was you said it does work with the paracorr taken out.

Don Pensack's article is a good resource re collimation. If you are looking for good basic gear for collimation, and already have a (non-barlowed) laser collimator (are you sure the laser itself is collimated?), then a sighttube and a chesire will get you "very good". Such "very good" will be more than enough if you have an f6 or slower scope. Excellent collimation would then, I'd argue, need the addition of an autocollimator for fine tuning the secondary as the final step. This would be particularly noticed if your scope is faster than f6, where the coma-free field of view is signficantly smaller and thereby more vulnerable to poor collimation.

I've got the full Catseye gear (sight-tube, chesire, autocollimator) and they are top. If you go that route, and also buy the Catseye mirror center mark, I'd suggest getting the "white" reflective triangle rather than the red. It's easier to collimate in the dark that way, and there is no real advantage to the red spot.