Collimation fun

[Astroman]

Hi guys,

In an attempt to get this collimation as good as I can, I need some help, pictures if possible of what the secondary mirror looks like, in a perfectly collimated 8" f/4 scope, looking down the Focuser. Mainly interested in what the reflections look like so I know how close the scope is to be collimated. I am trying to use CCD Inspector also, which has got me closer I think, but clouds have moved in now.

Any help appreciated.

I used Al's collimation program to center the secondary.. Pic below. But take the webcam away and the secondary looks like it's on an angle, I don't have a pic of that though, is this just an optical illusion?

[Peter.M]

Without tools, collimation of these is relatively difficult. I would think that looking down the focuser to collimate would be very rough. What you have done with Als col aid at the moment is center the secondary under the focuser, which is a good start.

I wouldnt use CCD inspector to collimate either, I find the results are too variable.

What you should see in the secondary when it is perfectly collimated is the main mirror and its clips, the reflection of the secondary mirror as a concentric circle and your eye.
http://starizona.com/acb/basics/images/collimation_perfect.jpg
that shows it pretty well

[Astroman]

Thanks Peter, Looks like the secondary look rather normal then, thats good to hear, I think I was being a little fussy about it's looks and second guessed myself...

[Astroman]

Ended up rechecking it all and redoing the secondary from scratch :D Then did the primary, only problems was the springs that hold the Primary mirrir cell, need to change these over one day.. Well It looked much better through a cheshire and sight tube so I rechecked in CCD Inspector and came up with this image below :) Rather happy with that...

[tlgerdes]

Sorry, why would you be happy with that CCD IS picture, that is as weird as they come.

Dark Blue = in focus
Light Blue = out of focus

This is telling me you have some weird inverted curvature happening, have a look at the 3D model of your picture in CCDIS

[Astroman]

Yep thats exactly right trevor, but I have no idea what I am looking at since this is all new to me. Still learning the ropes, and seeing something a little better than what I had before (I think) is a move in the right direction... Although star test confirms what you say, something is weird.

[Peter.M]

I think you will struggle to find a CCDIS image with a MPCC on one of these fast newts with less curvature than that.

If that were me, I would leave it as is Andrew.

[Paul Haese]

Hi Andrew, I have a couple of cats eye cheshires and centering tool you can borrow. Give me a call and we can sort out when we can meet.

[Astroman]

No worries Paul, will call soon, thanks for the offer, now to read up on how to use the cats eye LOL god I love this hobby, so much to learn :D