WANTED: Sight tube collimation device

[John K]

Just wondering if anyone has a sight tube collimation device for collimating a newtonian secondary and are keen to sell it?

[EzyStyles (Eric)]

Something like this John?

If you don't mind, the wire cross is bent and coming out. comes with cap.

$25.

[asimov (John)]

I made one using 2" exhaust tubing. 2" exhaust tubing needs to be lathed down slightly to fit the 2" focuser though. No crosshairs.

[janoskiss (Steve H)]

The secondary can be collimated accurately enough without a sighttube. The trick is to position your eye looking down the focuser so that the outer and inner ends of the focuser barrel appear concentric. If that is not possible for some reason with your focuser, then any tubing placed in the barrel will do - say unscrew the barrel from a cheap plossl. Then: 1) position the secondary so it looks centred and 2) orient the secondary so the reflection of the primary looks centred.

A Cheshire style sighttube collimator is more useful for the primary.