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Re: RE: Off Axis Optics

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Posted by Herb Teeuwe on January 4, 2001 01:12:35 UTC

I recently had occassion to clean/test and realign
an OA-4 from DGM engineering. The tube assembly
was one of the earlier units. After realigning the secondary and primary, I was able to achieve excellent in focus images. The diffraction pattern in this particular scope displayed excllent ring uniformity without any zones or turned edge. The rings were a bit softer outside of focus than inside. My seeing conditions that week were terrible, and this was certainly a part of the softness I spoke of. I returned the scope to its owner and am waiting to hear backfrom her on any improvements in performance. Mike Palermiti rates these scopes as being the finest
performers he has ever seen , including the best
APO's !
P.S. : My own fine 10" f/4.5 can be stopped down to an off-axis 4". The diffraction pattern
I see is as perfect as I can detect. Due to the poor seeing, I was unable to make direct comparisons between the two. (The DGM system,in addition, realigns the secondary and tilts the focuser to take full advantage of the off-axis mirror section.) Herb

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