Refractor Collimation

[Franklin]

How much of a deviation from spot on/perfect can the objective tilt be before it will noticably affect performance? I've read online that there is a certain amount of leeway in long focus instruments.

I have a 102mm f11 which has been giving good performance IMO but when I checked the collimation the other day it seems to be slightly off. The laser in the focuser is spot on central on the objective so that's fine but the reflections from the short Cheshire are not entirely concentric. It's not way off like a figure of eight or anything, the secondary reflection lies within the primary reflection but it is slightly off centre. I do not intend messing with it as the scope is quite new but I was just wondering if it is something I shoud be concerned about. It must have passed factory QC because it has a sticker on it saying so. Hopefully I'm just splitting hairs and I should just forget about it and enjoy the scope.🙂

[Knighty2112]

As long as your ‘frac is still producing pin sharp stars (when the atmosphere allows) then your f11 ‘frac will be fine. Not tested any of my ‘fracs for collimation, but as they all produce nice rounded pin sharp stars I am happy with them. Unless badly dropped or messed around with I don’t believe most ‘fracs would need collimation anyway.

[Franklin]

Thanks Gus, that's kind of what I was thinking. As it's new I don't want to mess with it. I've collimated a few achro's in the past but they had the 3 sets of push-pull screws on the front and it's pretty easy to adjust the tilt with those. But this one has 4 sets of 2 screws on the side and I haven't a clue what they do or how they work! 

The views of Saturn and Jupiter were good the other night upto 160x when the seeing allowed and they're very low down as well. I'll wait till the darker nights get here to try a star test. 🙂

[Piero]

I would run a star test on Polaris using 150-200x, first. F11 is quite forgiving.