Eyesight

I can't believe all these posts I've been reading concluding that the images in a Mak or Newt are comparable to an APO with respect to contrast and sharpness. Its physically impossible through the laws of physics. For those of you that can't tell the difference or quote a minimal variance, I say congratulations as you'll save alot of money. Some people's retina sensitivity to detail is is more challenged and/or the eyesight is not experienced enough from an astronomical perspective.

Rob

Are these conclusions based on *like*-aperture scopes, Rob?

I'm asking only because I honestly don't know which thread(s) you're referencing (they hold ZERO interest for me).

It's not impossible for *larger*-aperture scopes with secondary obstructions to equal or better smaller unobstructed scopes in the realm of image contrast and "sharpness."

Cheers and best wishes.
-Dan

Rob, what scopes are being compared here?

Sure, a 4" APO "should" be better than a 4" SCT, MAK or Reflector, but is that what's being compared here?

If you compare a 4" APO to a 7" MAK or a 6" Mak-Newtonian, hmmmm.... is the APO still better?

Please make reference to WHAT did you read... and WHERE... as you coming here with an attitude of disbelief does not necessarily make a point...

Also, saying that if somebody is NOT able to distinguish the difference it's because they have eyesight problems or not "good enough" astronomical knowledge, I think is plain rude and ignorant...


Clear skies,




Ivan

Rob, I just wrote about central obstruction and loss of contrast in newt and scts compared to refreactors.
Could you explain why a 6" refractor with 89' sq of aperture would have greater contrast than a 8" sct with 117.5"sq of aperture after the 26% central obstruction has been deducted?
I just dont' understand how this would be possible, with the laws of physics and all.
Floyd

Certainly, under ideal conditions the unobsructed
APO is the ideal scope. But in real world with
so-so seeing, etc, the differences are less pronounced.
Other night I was looking at Mars in the 6"
F/15 refractor and noticed the images were a
little off. I ran it out of focus and could see
half the aperture was blocked by leaves on a nearby
tree. Whenever this sort of thing happens, I'm
surprise how much aperture you need to block before
it becomes obvious something is wrong. Of course,
seeing is usually "average" which is not so great
around here; maybe on a really good night it would
be more obvious.

On an optical bench in controlled environment I
can usually tell you what the % obscuration is just
by looking at the in-focus Airy pattern. But
outside under the real stars its a completely
different story.