View Full Version here: : Major Collimation issue with my 12" Lightbridge
07-07-2012, 07:32 PM
I'm having a a major collimation issue with my 12" Lightbridge dob. I set it up the other day after lugging it back from a dark sky site to find that the primary mirror alignment is so far out that the return laser beam on my laser collimator doesn't even hit the secondary mirror. The primary mirror cell is obviously really out of alignment and I can't correct it with the collimation screws. I've had a look at the cell but can't see anything obvious. Does anyone have any suggestions on how to trouble shoot this problem?
07-07-2012, 07:46 PM
When you used your laser, did the laser hit the centre spot on the primary? Your post isn't clear on this. If it didn't the problem isn't with the cell of the primary mirror. It is either the alignment of the secondary or the secondary cage isn't seated properly.
07-07-2012, 07:51 PM
don't worry mate it can easily be brought back to collimation!!!!!!!!!!
i removed my mirror on my 16"lightbridge and cleaned it the other week and when i went back to collimate it i couldn't see the laser beam hitting my secondary..
first you are using a laser to collimate.if yes collimate the secondary to the donut on the primary mirror when centred release your 3 lock screws on the primary cell if you can't see the return red dot grab a piece of paper A4 size and hold it up beside the secondary and move it around till you see it on the paper then move your appropriate adjusting screws on the primary to bring it back to centre your laser collimater.re check your secondary again back onto the primary mirror then your primary back into collimater,i always check twice then tighten your primary screws that you loosened and all should be back to normal.....
hope this has helped
07-07-2012, 08:45 PM
Have a good look to check that primary mirror is sitting properly in the cell. Sounds like some major dislodgement has taken place. Don't be afraid to put your fingers on the edge and give it a good push in various directions to see what is going on.
07-07-2012, 09:08 PM
Also make sure that the laser itself is collimated. Put it in a V-block, aim it at a wall a few metres away and rotate the unit. If the dot makes a circular motion as you rotate it, then the laser itself needs adjusting.
07-07-2012, 09:39 PM
Thanks everyone ... great suggestions, I'll check the laser & position of the mirror tomorrow. FYI the laser hits the centre of the primary so I think the secondary mirror position is OK
07-07-2012, 10:03 PM
You've certainly been given some good tips there. Good luck with your beastie.
08-07-2012, 06:09 PM
If the laser is hitting the paper donut rather than the hole in the middle, the return beam will be very diffuse and hard to see.
17-07-2012, 02:56 PM
Thanks for the assistance. I removed & remounted the primary and that did the trick. Gave it a wash whilie was out. :)
17-07-2012, 08:41 PM
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