Quote:
Originally Posted by Legin
I have heard that the widest you should go is approximately 1/5th your focal length. Then you may get interference, I am not sure what you call it but basically the reflection of the primary mirror begins to appear in the eyepiece and can really ruin to wide a view.
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I'd say you're near optimum with the 28mm. It is likely with a 40 or 50mm eyepiece you will get a dark shadow in the middle caused by the secondary obstruction. It becomes more apparent with lower power eyepieces.