In article ,
Dennis Persyk wrote:

An obstructed scope may offer an advantage in splitting close doubles,
especially those of nearly equal magnitudes. The central obstruction
redistributes the power from the central dot of the Airy disc to the
first ring with respect to the unobstructed scope. This can give the
obstructed scope an advantage when viewing point sources. Of course
there is a corresponding disadvantage when observing extended targets.


Would the same apply if you placed an obstruction - say a dark disc - in
front of a refractor?

Jochen

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