From: Mel Bartels 
cc: ATM list 
Reply-To: Mel Bartels 


>     I'm going to paste below a discussion I've had with Roger Sinnott of
> S&T.  My question to this group is; Why is it possible to see planetary
> detail much smaller than a telescope's theoretical resolution?  Is the


It is not possible to see detail in a telescope that is below its
theoretical resolution.  No exceptions.  End of story.  By definition, a
physical impossibility.


A 2 inch scope can almost show Cassini's Division.  Double stars separated
by 1 arcsecond and of equal brightness and of apparent magnitude 3-5 in the
eyepiece will require in the range of a 5 inch scope to show the two
components.  Resolution of NGC891 takes a much larger scope.  In these and
in many more cases, theoretical resolution varies tremendously per type and
apparent size of object.

Ask yourself, how do you see a single star at night with the unaided eye?
The eye surely cannot resolve any of these stars, yet, there they are, to
use an ancient Greek metaphor, peering down at us.

Don't fall for the trap of believing that a 5 inch scope's resolution is 1
arcsecond detail, as that is its theoretical resolution for only one very
distinct category and condition of object.

Mel Bartels

--- BBBS/NT v4.00 MP