Collimation of 250 auto Skywatcher dob problems

[Eric the Halibut]

My Skywatcher 10" auto dob arrived last week. Unfortunately there were a few problems: 2 small dings in the tube; thumb screw in 1.25inch adapter broken in half but worst of all the telescope would not stay in any position below 45 degrees without falling back to the horizontal position and the motors would not function properly.

I had to send the offending panel back to OVL and received the replacement today. The scope works fine now but unfortunately they left out the handle and screws for the side panel. Do Skywatcher not have a QA department? These seem to be pretty elementary problems that a half decent QA system should have sorted out. I am now nervous about the long term reliability of the scope. Are Skywatcher telescope generally reliable?

Anyway the question I have is to do with Collimation. I read Astrobaby's guide and other Youtube videos on collimation and decided to try to collimate the scope today. I bought a Hotech lase collimator and also a Cheshire collimator for this purpose. When I attached the Hotech collimator and switched the laser on the collimation was way off. You could clearly see the laser beam shining through the tube and missing the secondary mirror when you held your hand up outside the tube. After a lot of fiddling I managed to get the secondary to line up with the primary centre spot and also got the primary to lilne up in the collimator. This proved to be a very worthwhile exercise as it showed me the mechanics of collimation which weren't as terrifying as I originally thought. I checked with the Cheshire and it seemed pretty good. My question is, when I put the home made colli cap (made from an old 35mm cannister as suggested) into the eyepiece, everything looks fine but I can't see all of the primary retaining clips. In fact the clips are outside the diameter of the view.

Is this something to worry about seeing that the primary and secondary appear to be well aligned to themselves. If it is a problem, I don't see how I could cure it because merely rotating the secondary mirror via the adjustment screws won't shrink the image so that the clips appear in the eyeiece unless I'm missing something. Thanks in anticipation.

[Peter Drew]

Hello Alex.

It might depend on the position of the focuser, the further "in" it is the more you will see of the mirror, further "out" and the secondary vignets the primary and you will not see the clips. Different manufacturers have different approaches to this balance depending on whether the scope is biased towards photography or visual.

[Eric the Halibut]

Thanks for that Peter you were spot on. I wound the focuser all the way in and bingo I can see all of the clips.

Mel's tutorial actually says 'Use a collimation cap in the focuser to force your eye central to the focus tube and rack the focuser tube as far out as possible.' Perhaps this should say 'as far in as possible.'