Bintel RC8 collimation

[Sammas]

My Bintel RC8's collimation is poor (yeah, I know ).

I've done a lot of browsing internet forums and the information ranges from "only ever adjust the secondary" to "strip the scope and adjust everything, but only if you have a tak collimation tool, an industrial lathe and a timespace nano-differentiator".

Then I read this: http://deepskyinstruments.com/truerc...re_Ver_1.0.pdf

Have not had a chance to give it a go yet (clouds, work, family, etc, etc)

Just wondering what other people's experience has been with collimating the RC8s? Adjust the secondary only, adjust both primary and secondary? Any tips or gotchas I should avoid?

[benklerk]

Hi Sammas

I have the 6" version RC. Few things
Do you have the tilt ring, a tak collimation tool and a howie laser or something similar?

Do not touch the primary if you don't have a tak tool, having one helps you to align the primary to the secondary mirror as the tak as concentric rings to align with.

The idea is, with the tilt ring you align the laser so its spot on in the middle of the secondary mirror (the secondary has a small black circle). Then you adjust the secondary so the laser beam falls back on ontop of its self. After that is done you check if the primary is still aligned with the secondary with the tak. If you need to adjust the primary you need to repeat the steps again.

This is how I do it on my 6" RC.

Ben

[kens (Ken)]

I've used the DSI method and I'm happy with it. But it is less convenient than the other methods and can use up valuable clear sky time. I like that it is a "what you see is what you get" method.
My tips: only adjust two of the three screws on primary and secondary and write down every adjustment you make in case you need to reverse what you've done. Plus you can check the total changes and because its iterative you can see if you are going in circles. And only make small changes each time. I also use the tilt ring to get the sensor squared up first.

[Sammas]

Brilliant - thanks for the feedback and great advice! Looks like the tilt ring is a key component in all this - do you have any recommendations on where to buy? Bintel has one for about $60 I think.

I'm much more confident about tweaking it now - and at the very least I can plug my laser in today to check how badly the focuser and secondary are out.

Great tips re: writing down the adjustments; thanks kens.

I don't have a tak or a howie laser (but I do have a laser) - I'm thinking I'll probably end up getting a tak (although I'm hoping I can get the collimation good enough without having to adjust the primary at this point).

[benklerk]

I have attached a picture on what it looks like when you have tak scope. You see all the rings? They need to be all concentric.
The other way is to defocus on a star and adjust the primary so the central obstruction is in the middle. After that you need to readjust the secondary and the tilt adjuster.

Are you still using the stock focuser? If you are they have a lot of moment and trying to align it makes it hard, I just had to replace my one and boy what a difference that made. Its solid as.

RC are one of the most hardest optical designs to adjust. If you don't have the right tools trying to align it is hard.

I got my tilt ring from bintel and its a must have to get a perfect alignment.

[Sammas]

Thanks for the photos - really very helpful. Of course I need to spend more money

I'll look into a new focuser too - I suspected that was an issue.

Amazing feedback. Thanks both very much.