Another collimation question

[75BC (Brendon)]

Hi All,

I have a newbie question with some backstory.

I did try to avoid getting some collimation knobs for my non edge C11 SCT. If you wonder why it’s because I’m a habitual fiddler. I heard that having knobs can make it tempting to play with collimation too much so didn’t want that temptation. Well that didn’t stop me putting my collimation out by said fiddling and I’ve never been able to get it back to where I should have just left it alone. It takes way too long adjusting those crappy little screws, not to mention the nervous sweat I break out in from holding a sharp object in front of the corrector plate in the dark. As I have so many other things that keep me from getting the time to do some observing and I was spending this precious time trying to collimate I thought "That it. I've had enough. My nerves are frayed. It’s time I bought some knobs". So I did. Not Bobs but some nice little stainless ones.

Finally to my question. With a star centralized in the eyepiece and I start to defocus I get a little mirror shift that I’m assuming is of a normal amount. What I want to know is do I re centre the defocused image?

The reason I ask is because I’ve noticed how much being off centre affects the position of the central shadow and any ‘squish’ to the rings of the defocused image. I’m getting myself confused though. Because I’m having to re centre after focusing and defocusing will my collimation be out relative to the re centring movement? Just seems I'm collimating in a different position to where best focus is. $h!t I’m confusing myself trying to explain it.

Is it;

a) You gradually collimate closer and closer to best focus so this is negated in the end anyway?

b) I may have too much mirror shift?

c) neither a or b?

Any help would be most appreciated.

[Merlin66 (Ken)]

Brenden,
Don't over think it......
I also have the Bob's knobs on a C 11 and haven't had to touch them in two years!
I'd suggest always getting into the habit of approaching focus from the same direction anti- clockwise and get as close to good collimation as you can.
Always do any adjustments with the star centered in the field of view.
Just enjoy the view........

[75BC (Brendon)]

Thanks Ken.

I was hoping someone would say something like that. I overdo, overthink, overworry...

I thought collimation would be something I'm good at as I'm pretty good with my hands but I wasn't with the dob I had before. I found it took a fair amount of practice before a connection was made between my brain and my eyes. I struggled away and literally like a switch was turned on it all just clicked and became easy. And that was just basic indoor collimating not star testing. Because SCT's are mostly done with stars in the dark I have a new learning curve to overcome but am not getting disheartened as I did with my dob at one stage because I know it's gonna 'click'.

And she does give beautiful views.