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I've had experience with several VC200Ls and know others who use them for imaging with dslrs or ccd or 35mm film (I have seen some truly great 35mm film pics taken with my older VC). The square/triangular star issue is not straight forward and does not appear to be related to the vane thickness. I have milled down the vanes on several VC200Ls- I have two VC200Ls converted to CF truss tubes and converted another for 'Bert'. One still exhibits squarish stars which appear to have been reduced by the thinner vanes (as you would expect). The other older scope does not exhibit square stars, thinned vanes or not - the thinner vanes for this one have merely tightened up the diffraction spikes, as one would expect. I know other VC200L owners who do not have the square star issue and have the original thick vanes.
Based on my experience and reports from other users I have seen, the most likely culprit for square or triangular stars is likely to be collimation, an inherent problem in the optics and/or mechanical issues affecting the optical components.
Lately I have been busy with other astro equipment so I have not gone back to tweaking my VCs to see if I can get rid of the square star effect in my 'finished' OTA. Too many astro toys and not enoguh time I guess.
I've attached a couple of pics of a VC200L CF truss conversion. This conversion is very rigid and makes collimation easier owing to the ability to see a laser dot on the secondary. It was not intended to make the OTA lighter.
Also the primary mirror has a special coating which plays a part in the hyperbolic optical configuration of the primary - perhaps this contributes to square stars? - the VC mirror has to be sent to Vixen to be specially recoated - a conventional coating adversely affects optical performance.
guy
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