is there anyone who lives near me with a good understanding of collimation procedures that may be willing to come around and try to sort a problem l am having?
l have an f/5 newt that l am having trouble with, l am collimating with a Howie Glatter laser collimator, l can get perfect alignment according to the instructions but still have elongated stars, tweak the primary and the elongation gets better but by no means perfect, and this is with a Baader MPCC.
when the primary is tweaked this obviously throws out the laser but the stars get better so that is the puzzle, could anyone spare some time to give me a hand with this problem. thanks.
It's a little difficult to explain but the secondary should be a few mm both toward the primary and a few mm away from the focuser.
I have looked at my Skywatcher 12" and it looks factory offset, ie: the center shaft support for the secondary is not attached to the physical center of the mirror but slightly towards the upper edge. So naturally the secondary mount is dead center of the OTA but because of the off set mounting it is away from the focuser.
A bit of a read but great inpho..... http://www.atmsite.org/contrib/Carlin/collimation/
Hi Mick.
Check to see if the focuser is squared in relation to the tube..test this by placing the laser in the focuser then focusing fully in and out whilst viewing the laserdot on the primary mirror...if the laserdot moves then the focuser needs to be squared.
Cheers!
checked the focuser and it seems perfect focuser racked in and out and beam does not move of centre. l've attached a couple of enlarged pics one from the centre of field and one from the edge. baader mpcc used with 400d.
A bit hard to say but the collimation is out. Can you do a bright star dead center of the frame with the out of focus disc covering 1/2 to 1/3 of the frame?
What is the specs of the scope?
Yep she's out. Use a 3-5mm eyepiece while on the star and de-focus it and collimate the primary until the center shadow is perfectly centred in the disk. the diffraction rings around the disk should be perfectly concentric and evenly spaced.
Mick, I've held off making any suggestions as you stipulated at the outset "good understanding", and I'm basic at best.
The latest image does indeed look slightly off.
Couple of things to ponder. I sometimes use the laser to get the secondary pointed at the primary, but normally use the cheshire and star to finish the primary, not the laser.
In my case (and possibly yours, you image and don't observe as much, correct? If so, using an eyepiece to collimate may result in the result looking good, but when you put the camera, CFW, extension tubes, etc, etc, on maybe this changes?? Another option is to collimate with the webcam in place, although this will be lighter than the imaging unit I suspect.
Good luck,
Gary
thanks Gary, my initial problem was when collimating with the laser (Glatter Laser, supposedly one of the best), it came up spot on but when imaging you get the result in the pic.
l will try a couple of methods when it clears and let you know how l get on, thanks for the reply.
