RE: ATM Performance with Spherical Aberration

["Arjan te Marvelde (EMN)" <Arjan.te.Marvelde@emn.ericsson.se>]

: > So, to get back to your question, i'd say that the smaller 
: > exit pupil yields higher contrast with the same mirror, 
: > but the larger mirror should still give more light with the 
: > same exit pupil. So i'd expect that the bigger scope should 
: > give higher brightness with comparable contrast in the 
: > questioned case .
: 
: Hmmm, not sure ???
: The present case, a 36" F/13 scope appears to have been 
: configured with same magnification as a 20" F/5. The 
: observation is that the image is dimmer in the 36". The 
: exit pupil is twice as big in the 36" calculated by 
: dividing appropriate eyepiece focal length for 300x 
: by system focal ratio. 

So, apparently something must be wrong with it.

/arjan