When I do an alignment, I check for centering using a target taped over the objective with a pin hole in the exact center. I make the adjustments till the laser comes through the pinhole which I can observe in a mirror on the far wall. I then rotate the tube in the rings to make sure the spot on the wall does not wobble. If it does, I check for centering of the objective and the target. Ideally, the laser will exit the pinhole and stay stationary on the wall when the ota is rotated. I use a helical centering device in the 2" focuser to insure that the laser is precisely centered in the focuser. Once this is adjusted and aligned, I then insert the diagonal into the focuser and the laser into the diagonal. I then shim or adjust the diagonal in the focuser until I again have the laser exiting the
pinhole. At this point, I lock down / tighten the diagonal in place without the centering device. At this point, the optical train from the diagonal to the objective should be aligned. Collimation of the objective (tilt) is now adjusted using the rotating ota method and confirmed with a cheshire. Final adjustment is made out under the stars with a bright star and observing the diffraction ring pattern. Obviously, you can not rotate the diagonal in the focuser and maintain this precise alignment so I use rotatable focusers. I always check the alignment while rotating the focuser to confirm it is correctly manufactured, If not, it goes back for an exchange. Most of the new GSO crayfords seem to be pretty good for this as are the WO's.
I know this is not absolutely perfect, but it seems to work for me (close enough) and only needs to be done once or twice a year - ususally when temperature changes such as fall to winter and winter spring to summer.
Warp
--- On Wed, 7/8/09, WayneG. <im66skidoo@...> wrote:
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