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Optical quality Matters Not?

Started by rumpledoll, 06/06/2006 10:13AM
Posted 06/06/2006 10:13AM Opening Post
I have seen in several places the assertion that the optical quality of binoviewers does not matter in a practical sense. As I understand it the claim, it is saying that ALL prisms and beam spliters from the least expensive to most expensive binoviewers currently extant are above the minimal quality which would be visible to any observer.

I do not agree with this claim in principle. My hypothesis is that the surfaces of the beamsplitter and the lower portions of the prisms are far enough from the focal plane that a good portion of the surface is used to form each point on the image. Hence, quality matters and differences can be seen.

I do not have more than one binoviewer, so I cannot test either hypothesis.

Anyone done such a test at high powers (i.e. smaller focal length eyepieces) or have anything to add as to why one might or might not see any such differences?

Philip
Posted 06/06/2006 10:43AM #1
See message #448699 for someone who seems to agree with you...

Jon
Posted 06/06/2006 11:21AM #2
I've used both the Zeiss/Baader and Denk II. The former has
better optics -- I cannot see any deformations in the star
test. Whereas the Denk II had small but definit aberrations
at high power -- say a 7mm eyepiece in F/8 beam and no Barlow.
But if you stay away from short eyepieces (>=12mm) and use a Barlow,
then I agree the differences would vanish.

In general I would say binoviewing is best done with
longer eyepieces (more eyerelief, more comfort, less taxing
on bino collimation) anyway, so the differences I mention
are nearly moot.

I guess in complete fairness I should add that when I first
got the Zeiss unit there were also aberrations which I traced
to the non-Zeiss right angle prism AP was supplying with these,
which I have since replaced.


I have seen in several places the assertion that the optical quality of binoviewers does not matter in a practical sense. As I understand it the claim, it is saying that ALL prisms and beam spliters from the least expensive to most expensive binoviewers currently extant are above the minimal quality which would be visible to any observer.

I do not agree with this claim in principle. My hypothesis is that the surfaces of the beamsplitter and the lower portions of the prisms are far enough from the focal plane that a good portion of the surface is used to form each point on the image. Hence, quality matters and differences can be seen.

I do not have more than one binoviewer, so I cannot test either hypothesis.

Anyone done such a test at high powers (i.e. smaller focal length eyepieces) or have anything to add as to why one might or might not see any such differences?

Philip