Quote:
Originally Posted by Satchmo
I don't think its accurate to say that an instrument with 1/2 wave spherical aberration does not focus. Anyone owning a high quality optic with a 50% obstruction is seeing an in focus Airy Pattern similar to an unobstructed telescope with 1/2 a wave of spherical aberration.....
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Well, OK, it does focus, just not very well.
Sure, with the "best focus" airy disks are similar with 50% obstructed systems and say unobstructed 1/2 wave error system.
But what I've found time and time again with imaging, that's not the whole story...the system with the error has a more divergent "off focus" spread, scattering or both which is significantly larger than the airy disk and seeing nearly always turns into halos....something you don't get with a well corrected system.
Hope that makes sense
