Quote:
|
Originally Posted by Mark Suchting
I wouldn't say `kill' but SCT's usually suffer from rough optical surfaces and the 40% obstruction at the secondary baffle lowers image contrast significantly over the smaller Newt obstruction. A 33% obstruction for example lowers the contrast curves equivelent to an unobstructed system with about 1/2 wave wavefront error. Throw in some surface roughness , and real optical errors and even good SCT's are struggling to get a Strehl ration in the low 0.70's. A well made Newtonian with small obstruction and single smooth primary surface can easily keep a Strehl above 0.95 ( Strehl ratio of a perfect system is 1.0).
Mark
|
So out of curiosity, what kind of difference would this difference in Strehl ratio translate in terms of difference in observable magnitude? Another way of asking is, for a visual observer what difference might a "reasonably skilled" observer notice?
Thanks!