Seben colimator - way out

[adaregazer]

Greetings! I recently bought one of those cheap Seben laser colimators and I thought before making any adjustments I thought I would check the device itself. It seems to be way out of alignment. I found this by putting it in a jig and rotating it. I have located the three alignment screws so I will have a go at aligning it myself! Anyway I have ordered a Cheshire so if I can align the seben I can use it in the field. Anyone else had problems with seben colimator? it seems wrong that a company can sell on products that are defective and it seems everyone on the net knows it too.

[OzStarGazer]

No, mine was fine when I bought it. I checked it like you did (in a similar way).

[cometcatcher]

I recently bought a "next generation" laser collimator. Yep it was out by a mile. Also found the 3 screws behind some silicon glop. But the switch is dodgy on it so it's next to useless.

[knightrider]

I also have a "next generation" laser collimator which much the sdame as the Seben. Same story, it was out of whack when rotated, I collimated it in the jig I made.

I wondered why my Cheshire and Laser would never agree with each other. This was why, but my additional reason was the focuser had it's own set of collimation screws too. Once I got all three to agree with each I was happy.

Unfortunately this seems to be a trait of the cheap laser collimators. You get what you pay for I guess. At least they have provision to collimate them to be useful again.

[FrankyT]

I have given my laser collimator the flick. I now use a 35mm film canister with the bottom cut out of it and a small hole in the centre of the cap. It works great but not so easy in the dark. I purchased a Cheshire collimator but the canister works just as good. The skywatcher telescope manual shows how to use it. Work in small steps.

[JB80]

I got a Seben collimator for Christmas and it's fine, I tend to use it as a compliment to my Chesire.

That said once I spin the laser 180° in the focuser it moves off centre which leads me to believe the focuser is off whack and I can't work out how to fix that so might just upgrade my focuser.

[knightrider]

The OP mentioned there are 3 alignment grub screws that you can tweak to re-align the collimator.

Make a V shaped jig and strap the laser in there, perhaps with a rubber band or hairband. Fix the jig down so it doesn't move. Have the dot hit a piece of paper a few meters away and rotate the laser.

As you rotate it you should notice the dot move around in a circular pattern. Record the circle, find the centre of the circle and mark it out on the paper.

Then as you make your adjustments, aim to have the dot stationary on the centre mark as it's rotated.

[JB80]

The collimator isn't out though, I had checked this already. The focuser appears to be the issue or at least I think it's that. My star test looks alright so I'm going to live with it a bit longer and see what happens.

[knightrider]

Interesting. Does your focuser have adjustments on the base to align it? Mine has 3 grub screws to align it, then secondary grub screws to lock it in place. Same way the mirror collimation screws work.