Collimation confusion.

[iainmax]

Hi again.

Thank you for recommending Astro Baby's guide to collimation ( http://astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm) It is a great a great tutorial but i've hit upon a problem.

Here's what i've managed to achieve so far.

I've managed step one :The Spider Vanes and Secondary Mirror Holder. All done and i'm happy with that step.

I've managed step two:The Secondary Mirror / Focus Tube Alignment I can achieve a near perfect circle when viewing through the focuser tube. The main screw and tilt adjusters are tightened.

Step three: The Secondary Mirror/Primary Mirror Alignment. This is where I am confused. After completing step two and tightening everything up, I am then asked to undo those same screws/bolts in order to align the secondary to the primary mirror. This doesn't make sense as I will then undo the calibration achieved in step two.

Have I missed something? It's probably something glaringly obvious but i'm stuck! I want to be able to perform these tasks myself and learn from my mistakes which is why i'm resisting the temptation to let someone else do it for me at the moment. Hopefully, collimation will become second-nature to me and I appreciate your help greatly. 

Iain

[kalasinman]

Leave the center bolt in the secondary holder snugged, then  trade off loosening one of the 3 screws and tightening the other 2, or vice versa to get the secondary to primary. I've heard it likened to the legs of a 3 legged stool. Adjust them in smal increments, so none of them is too loose. You can end up with each close to tight and the proper alignment too. Then the primary last. I use an alignment cap for the first 2 stages, then switch to a (carefully colimated) laser for the last 2, then a final check with the cap.

[iainmax]

Thanks kalasinman. I shall give that a try this evening.

Iain

[iainmax]

Well, i think I may have successfully colllimated my telescope for the first time. Everything seems to line up perfectly. I guess the best test is to wait for dark and see what Polaris looks like through the viewfinder. Fingers crossed!

[LukeSkywatcher]

Can you point a camera down the focuser and take a quick image?. Dont use the flash. 

[-Aldebaran-]

If your collimation was off quite alot on your last observing session then you'll notice a considerable improvement if you collimated correctly.

I always have issues with secondary mirror adjustments, the main issue is touching it when not necessary!! I've found that loosening the three grub screws too much causes slack in the centre bolt and I have to fall back to step 1.

It gets easier and quicker to collimate once you've been over it a few times.