Re: Refractors vs. binoculars

On Tue, 14 Feb 2006 20:12:07 -0800, Brian Tung wrote:

Tom Rauschenbach wrote:
I just got a pair of Oberwerk 11X70 binoculars on a decent mount.

Orion's belt just fits in the field of view and the sword is magnificent,
with the Trapezuim stars easily visible (unless I am sorely mistaken).

It's possible. It is darned hard to resolve all four stars of the
Trap at 11x. I'm pretty sure I couldn't do it--I'd probably need
at least 15x, and my vision is fairly acute. At any rate, I certainly
wouldn't call it easy.


As I said in my response to Doink, I could only confidently resolve three
stars. I was thinking it was the Trapezium based on the the context.
It seemed to be the right stuff in the right relationship to stuff
around it. I'm ready to have been wrong, but it sure doesn't seem like I
am this time.

But I notice that the amount of CA is a lot less than what
I've seen in
Acromatic refractors. I can't say that I've ever used an APO. But I
have to wonder why the performance of binoculars seems to beat simple
refractors.

I'd be pretty surprised if you could see much CA in M42. Actually,
what's more likely a problem in binoculars is substantial lateral CA,
not the longitudinal CA that's the difference between apos and achros.
Take a look at the Moon in these binoculars. Move the Moon back and
forth in the field of view. Any color fringing there? How does it
change as it moves from side to side?

And now you get to me question! The amount of purple fringe I see in
the binos is just way smaller than what I've seen in refractors costing
much more than these binos. I'm just wondering why these things perform
so much better than I can explain.




I think I understand that the central obstruction of my SCT costs me a
lot of contrast, but the lack of of wierd color effects in the binos
puzzles me.

Look at Venus, when it next comes around. That's a fairly harsh test.
So's the Moon.

Right now now the moon is so bright that could be the reason I'm not
seeing the optically defects of these binos. I will take you suggestion
and examine venus poste haste.


I'm thinking at a pair of 22X100 binos would be a better bet for a grab
and go scope than a 4 inch refractor and a lot cheaper. But that seems
economicaly wrong to me.

It's less flexible, and it requires a mount. Not saying there aren't
times when a big bino is worthwhile--some comet-watchers swear by them--
but to me, a lower-power bino makes more sense to me.

The 11X70s were chosen because for both parameters they are the most one
can expect to use hand held. And they are right on the edge, hand held.
On a mount, they are really nice to use. They mount I have is rated at
four times their weight. Vibration seems not to be a problem. Which
makes sense to me. But the color of the stars is just so much better than
I had expected that I'm wondering what is going on.




By the way, mostly refractor owners think the CO makes a big difference
in terms of contrast. Those of us who own all types and have egos large
enough not to require boosting <g> have more moderate beliefs on the
matter.

The difference I see in contrast has nothing to do with my ego. I would
have loved to go on thinking that my SCT suffers little from its central
obstruction, and that catadioptric telescopes are fine performers. But
this $300 binocular is doing things that a $1500 SCT can't do. Granted,
11X is a different world than the 100X to 300X neighborhood of the SCT and
I know that this bino can't show me the things a real telescope can.

But I still wonder why it is so free of the strange color artifacts that
I've seen in refractors.

That's the real question.


.

Relevant Pages

  • Re: Refractors vs. binoculars
    ... what's more likely a problem in binoculars is substantial lateral CA, ... Take a look at the Moon in these binoculars. ... the binos is just way smaller than what I've seen in refractors costing ... much more than these binos. ...
    (sci.astro.amateur)
  • Re: Good Binoculars Around $60?
    ... viewing the night sky. ... I don't remember if I can see M110 in our 7x50 binos or not, ... that you can easily resolve individual stars. ... clouds, dark nebulae, double stars, Moon). ...
    (sci.astro.amateur)
  • Re: Refractors vs. Bino optics redux
    ... I'm still puzzled over the ecomonics of big binos versus refractors. ... binoculars is inexplicably less expensive than a single refracting OTA. ... You can see that the price for the ED telescope you show, ...
    (sci.astro.amateur)
  • Refractors vs. Bino optics redux
    ... I'm still puzzled over the ecomonics of big binos versus refractors. ...
    (sci.astro.amateur)
  • Re: Refractors vs. binoculars
    ... guess that the three brighter stars of the Trap would appear to be a ... much more than these binos. ... My guess is that the low power is the main issue, ... this $300 binocular is doing things that a $1500 SCT can't do. ...
    (sci.astro.amateur)
Quantcast