Squaring the focuser

[Karen]

After collimating my Skywatcher 10inch flextube the secondary mirror is never quite central in the Cheshire sight tube, it's always slightly shifted towards 10 o'clock. Everything else is spot on, spider vanes centered, primary mirror centered in secondary etc.

So I thought I would have a go at checking if the focuser was square in the tube. Firstly I took some careful measurements at various reference points on the focuser body and tube. Then I transfered these to the opposite side of the tube to find where the dead center of the focuser would be. I marked this whith a piece of sticky paper and placed a dot dead center.( See Picture)

I removed the secondary mirror having already done a risk assessment where to safely put the mirror out of harms way!

Next I put the cheshire in the focuser. A laser might have been better but I don't have one. My center spot was about 4mm off the crosshairs so the focuser was indeed off square.

Adjusting the focuser collimation on this 'scope is the same as collimating a primary mirror, with three adjusting screws and three locking screws. (See picture with allen keys inserted) So aligned the crosshairs on the center spot, re-assembled and re-collimated the mirrors and now everything is centered perfectly.

[jimmyjamjoejoe]

I recently had to do this straight out the box. The scope was out of collimation and the focuser wasn't square, which made my first attempt at collimation a bit of a nightmare!

I'm glad it happened though, since now i know the ins and outs like the back of my hand

[Karen]

I really enjoy this collimation thing. I find it very therapeutic

[earth titan]

I really enjoy this collimation thing. I find it very therapeutic

Am I glad to hear someone else say that. Me to!