Laser collimators inaccurate?

[Tlawrence84]

I placed my laser collimator in my new 250px Dob, and the red sight is just off the collimating ring on the mirror at the top (at the 12 o'clock position). If I rotate the collimator 180 degrees, then the laser dot is at about the 11 o'clock position just above the circle.

It doesn't seem to sit perfectly straight in the eyesight tube, is this a trait of laser collimators? A trait of an adequate (but not massively) focuser? Looking down the eye sight to get a rough idea of collimating, it appears to be fairly lined up...

I think I'm going to order a premium Cheshire from FLO but don't want to if the lasers are usually good enough. I'm expecting to get a lot of use from a collimator with a flextube dobsonian tho.

[Ags]

You have to collimate your collimator. The laser needs to be pointing directly down the focal path. If you google "collimating a laser collimator" your will find this:

[Tinker1947]

Have you checked the laser to see it is collimated.......

[Tlawrence84]

Oops, seems like a fairly basic oversight on my part! Will check that out now. Not much else to do with these damn clouds!

Thanks guys

[Tlawrence84]

Thanks for the above video link. Something for owners of Skywatcher Laser Collimators to be aware of, it does have collimating screws, you have to break open the rubber 'cover' over them (it doesn't look like it's there, but poke it if you don't believe me!)

[andyman]

If the laser is collimated there is also slop in the focusser that could be throwing the beam off when tightening. put the laser in the focusser tube and wiggle it...if there is alot of play this could be part of the problem.if there is... you could put insulation tape around the barrel to make it a tighter fit in the focusser tube.this is why i dont use a laser for the secondary only the primary.... throws up too many problems