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hi ColHut,
I bought a two-inch diameter Kendrick laser collimator <http://www.adorama.com/KDLC2.html> for about $150 Canadian (I was in Canada at the time). The Kendrick collimator has a removable conical/45° section that is very useful when collimating (returned laser beam may be viewed from the mirror box end of my 15 inch Dob when collimating and it has a removable ultra-thin Barlow lens built-in which allows the use of the Barlowed-laser technique when collimating a Newtonian design. Regarding the former (conical/45° section) I don't sit at the mirror box end and collimate by looking up through the truss tubes anymore. I have set up a small webcam (by clamping it onto the secondary spider vanes and aims at the inside of the Kendrick collimator to see where the returned beam is shining) which displays the returned laser beam on a laptop computer screen while I sit and fiddle with the collimation adjustment. Once initial collimation is done (ie, the returned laser beam is seen to disappear down the hole in the conical/45° section of the Kendrick laser, I then fit the Barlowed section to the collimator body and centre the reflected image of the hole-reinforcement which sits concentric with the exact centre of the primary mirror. The Barlowed-laser technique requires the image (a doughnut) to be concentric with the exit hole from the laser barrel itself. It is hard to explain but if you are interested, have a look at the Nils Olaf Carlin article in Sky and Telescope <http://gmpexpress.net/~tomhole/blaser.pdf>.
Have fun,
Doug
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