Collimation Probs -

[shaneaust]

Hey all:

I'm embarrassed about this - got to collimating my scope last nite and now when I look down my homemade focusing-tube, what I see is the attached.

What have I done??!! I've tried collimating the secondary mirror and the primary, re-positioning the primary, etc, etc...all to no avail.

Any ideas as to whats wrong??

[shaneaust]

Hey, thanks for all the helpful suggestions! (yeah, I'm being sarcastic...). I finally was able to tweak the secondary and got it lined up properly. Took ages. But I guess doing it that way, I learned something.

[Kokatha man]

Hi Shane - after seeing your post I thought somebody ought to at least acknowledge it, even if you've sorted it out in the interim! Not getting any responses is pretty darn frustrating: but I'd have to defend most IIS members and suggest it was just "one of those times."

My own experiences of getting back into collimating after a 30 odd year break were similarly frustrating - and your final comments are spot on, the piccies and advice are just no substitute for learning the hard way! Of course, the luxury of having someone next to you with the patience and ability to show/teach would be super, and learning by yourself still requires you to remember just how you did get/jag it right!!!

From your first post's diagram it looks like the secondary was then aligned and the primary needed adjusting - though when you spoke of repositioning the "primary" I presume you meant "secondary"?

I actually deliberately put my secondary out of position as well as alignment to make myself re-learn the whole process - a sort of sink or "swim you *******" challenge to myself.

I used, to really get on top of the collimating process, an Orion combo sight tube/chesire collimator (about $70, and no, I aint got shares in the company!)

What I found, after re-positioning the secondary by making sure it was centred in the scope tube (ie the spider was centred in the tube) and then making sure the secondary mirror was centred when looking down the focusser tube (centred in the focusser tube's view) AND also turned/rotated so it (the secondary) presented itself as being as near as possible to looking as if it was "round" (as opposed to the fact it is actually oval) THEN you fiddle with the secondary's adjusting screws to get to AS NEAR AS YOU CAN to where your diagram indicates - "bob's knobs" type screws certainly make this bit so much bloody easier!

Then it's down to the primary to move that small circular reflection with its cross towards the centre of the whole shebang - BUT in actual practice I found that after fiddling with the primary I then had to go back and do some more fiddling/adjusting on the secondary (including re-rotating it to get the round appearance, which meant re-adjusting its screws again, cos rotating it requires you to loosen off the screws that you've just tweaked!) and then back to the primary again - 3 or 4 back and forths till bingo, it was all aligned. Subsequent star tests to reveal diffraction rings revealed it to be spot on: since then its been only a tiny tweaking of the secondary to maintain (unless something untoward hapens....!)

Hope this helps, and "bob's knobs" or your own (cheaper) version of these is so bloody helpfull with all the above (no shares there either!)
Cheers, Darryl.

[edwardsdj]

Hi shaneaust,

Sorry to hear you've been having problems with collimation :(

Glad to hear you got it sorted in the end :)

You've probably seen this but there is a great instructional video here http://www.andysshotglass.com/Collimating.html

As Darryl said, collimation knobs (Bob's Knobs from Bintel) help a lot. I got the primary and secondary knobs and the stiffer springs. These let you collimate without tools. The stiffer springs prevent the collimation from shifting as you change the altitude of the scope.

Have fun,
Doug

[Kokatha man]

Hi again Shane - that last bit should have read "only a bit of tweaking of the primary" - to keep it collimated after getting it all "A" ok: to date my secondary hasn't required any more adjustment; and as I understand it shouldn't need such (in general.)

Cheers, Darryl.
ps my newt scope's the same unit as yours

[Outbackmanyep]

I guess most of us were watching the cricket!!!
Don't worry though, i've been in that boat before! Glad you got it sorted!
You sorted it out in the 10 minutes since your first post though, which is a great effort!!
Apologies to you!!

Cheers!:thumbsup:

[shaneaust]

Thanks to you all for responding - my somewhat sarcastic comment in my 2nd post was just tongue-in-cheek...I don't expect people to jump to help me (nor am I one to do it! I've given very few hints on here!).
But - appreciate all your feedback. What happened is that I had not used the scope in quite awhile and had just forgot how to make collimation adjustments - I have a short-term memory like a sieve!