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Equipment Discussions >> Binoculars

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mv1612
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Reged: 08/11/09

Re: 7x35 binoculars for viewing the stars? new [Re: KennyJ]
      #5559860 - 12/07/12 07:38 PM

I understand the difference between TFOV and AFOV, no problem with that (I'm just in the process of changing the eyepieces for my dob, because I want a larger field of view). I know that I would't use a 48 deg eyepiece on my scope. But I'm not sure if the sensation is equivalent, the same AFOV in the eyepiece of a telescope or on a binocular (I don't have any experience whatsoever with binoculars).

I think I will still buy the 6x Yosemite. The exit pupil on the 8x is too small if it is to be used for the night sky, I think. I will take a decision as soon as possible...

Thanks for your help, it was invaluable.

Virgil.


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Tony Flanders
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Re: 7x35 binoculars for viewing the stars? new [Re: mv1612]
      #5560473 - 12/08/12 07:33 AM

Quote:

The exit pupil on the 8x is too small if it is to be used for the night sky, I think.




I don't agree at all. For any given aperture, smaller exit pupils will almost always show you more. 8x30 binoculars will show you much fainter objects and much greater detail in small objects than 6x30s.

Note that with interchangeable-eyepiece telescopes, where there's complete freedom of choice, most people choose exit pupils of 2.5 mm or smaller. In 30-mm binoculars, that would translate to 12x30.

The main reason to prefer lower magnifications (i.e. bigger exit pupils) is true field of view. But that's less true in this particular case than in most.

Also, some people find the less-bright view through a smaller exit pupil less aesthetically appealing. I can't argue with that since it's an entirely subjective judgment.


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Mark9473
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Re: 7x35 binoculars for viewing the stars? new [Re: Tony Flanders]
      #5560541 - 12/08/12 09:02 AM

The point is, Tony, not that 8x30 shows you more than 6x30 - which is true - but that an 8x30 has a rather small exit pupil compared to e.g. 8x40 or 8x50 binoculars.

One of the key attributes of binocular viewing is the way two-eyed viewing reacts to bright colourful images. A 3.75mm exit pupil is borderline for that, if not already too small.


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Tony Flanders
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Re: 7x35 binoculars for viewing the stars? new [Re: Mark9473]
      #5560570 - 12/08/12 09:32 AM

Quote:

The point is, Tony, not that 8x30 shows you more than 6x30 - which is true - but that an 8x30 has a rather small exit pupil compared to e.g. 8x40 or 8x50 binoculars.

One of the key attributes of binocular viewing is the way two-eyed viewing reacts to bright colourful images. A 3.75mm exit pupil is borderline for that, if not already too small.




I'm not entirely sure what you're saying. If you are repeating my previous point, that some people find the brighter image more aesthetically pleasing, I can't argue with that.

On the other hand, there was a recent thread in this group lamenting the fact that it's so hard to find binoculars with 4-mm exit pupils, which the poster (and many others) felt gave the best possible compromise between field of view, brightness, and optical quality -- the point being that almost everybody's eyes show much sharper images when masked down to 4 mm. Again, that's an aesthetic preference, impossible to argue with.

But if you're saying that the benefit of two-eyed viewing over one-eyed viewing decreases for smaller exit pupils, that's demonstrably incorrect.

As for color, the only things in the night sky that appear colored are stars, the bright planets, the Moon (to a small extent) and a handful of nebulae. All of those will appear more colorful, not less, in 8x30s than in 6x30s.

Are you making your statement based on direct experience or hearsay?

Edited by Tony Flanders (12/08/12 09:37 AM)


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Mark9473
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Re: 7x35 binoculars for viewing the stars? new [Re: Tony Flanders]
      #5560596 - 12/08/12 09:55 AM

My direct personal experience is that star colours are more vivid with larger exit pupils.

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mv1612
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Re: 7x35 binoculars for viewing the stars? new [Re: Tony Flanders]
      #5560689 - 12/08/12 11:04 AM

I'm not sure I understand. Exit pupil is directly related to the perceveid brightness of the objects you observe. For example, in a telescope, if you're looking at an extended object, the 7mm EP gives you 100% surface brightness and for example a 5mm EP gives 50% and a 3mm EP gives 18% of what is possible with that particular telescope.

Then of course going with a smaller EP gives you more detail and increases the contrast because a darker background sky is achievable (we're not talking here about completely dark places). Based on this I was thinking that a 5mm EP is better than a 3.75 EP, especially for a child that would theoretically be able to achieve 7mm EP.

Let's put it this way. If I look at the Pleiades, the double cluster, or just the Milky Way, which one of these two binoculars would give me more pleasing views? And let's define pleasing: bright, sharp, spectacular, groupings of stars.

If I try Andromeda galaxy: in which one of these two will it be easier to notice something?

Or is the answer entirely subjective?

I also feel kind of guilty trying to use 30-35mm bins for astronomy, I know I'm streching things here, but it's just my situation for the moment... Thanks for understanding.

Virgil.


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mv1612
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Re: 7x35 binoculars for viewing the stars? new [Re: mv1612]
      #5560700 - 12/08/12 11:11 AM

Another question: in which one of these two will I be able to see fainter stars?

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Mark9473
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Re: 7x35 binoculars for viewing the stars? new [Re: mv1612]
      #5560715 - 12/08/12 11:21 AM

A 7x35 and 8x30, if of equal optical quality, are tied as far as limiting magnitude goes. There are a few targets, notably partially resolved open clusters, where the 8x will show a little bit better resolution. The main disadvantage of 7x in my opinion is that on the Moon you'll see noticeably less detail than at 8x.

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Mark9473
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Re: 7x35 binoculars for viewing the stars? new [Re: mv1612]
      #5560720 - 12/08/12 11:24 AM

Quote:

If I look at the Pleiades, the double cluster, or just the Milky Way, which one of these two binoculars would give me more pleasing views? And let's define pleasing: bright, sharp, spectacular, groupings of stars.




Pleiades - tied.
Double Cluster - the 8x30 will be better.
Milky Way - the 7x35 will be better especially since it has a much wider FOV.


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mv1612
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Re: 7x35 binoculars for viewing the stars? new [Re: Mark9473]
      #5560729 - 12/08/12 11:28 AM

Sorry for the misunderstanding: I was talking about the two Yosemites: 6x30 versus 8x30. Thanks

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Mark9473
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Re: 7x35 binoculars for viewing the stars? new [Re: mv1612]
      #5560752 - 12/08/12 11:40 AM

Well personally I would not get anything below 7x as it will show virtually no resolution on open clusters and far too little detail on the Moon.

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Binojunky
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Re: 7x35 binoculars for viewing the stars? new [Re: Mark9473]
      #5560841 - 12/08/12 12:50 PM

Regarding the Yosemite, the odd bad one gets out so if buying be aware that a good return policy is needed also if like me they had to be returned to Leupold from Canada that you will be on the hook for shipping both ways, that makes an inexpensive binocular not such a great bargain, DA.

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Tony Flanders
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Re: 7x35 binoculars for viewing the stars? new [Re: Mark9473]
      #5561289 - 12/08/12 06:08 PM

Quote:

My direct personal experience is that star colours are more vivid with larger exit pupils.




Are you holding magnification or aperture constant?

In general, if you hold magnification constant, larger exit pupils always show more, because they increase the aperture. So 10x50s invariably show more of everything than 10x30s of identical optical quality.

But if you hold aperture constant, larger exit pupils decrease the magnification, and therefore show less. So 7x50s show less than 10x50s.

Star colors are generally more saturated in larger apertures. So 10x50s show more colorful stars than 10x30s. That's a function of aperture, not exit pupil.


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Tony Flanders
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Re: 7x35 binoculars for viewing the stars? new [Re: mv1612]
      #5561290 - 12/08/12 06:11 PM

Quote:

Another question: in which one of these two will I be able to see fainter stars?




8x30s will show considerably fainter stars than 6x30s. My own 10x30s will show even fainter stars than that. By a fair margin.

For showing stars, the Bishop formula is a pretty good approximation -- multiply the aperture by the magnification. So 8x30s show roughly as many stars as 6x40s.


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Tony Flanders
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Re: 7x35 binoculars for viewing the stars? new [Re: mv1612]
      #5561291 - 12/08/12 06:16 PM

Quote:

Let's put it this way. If I look at the Pleiades, the double cluster, or just the Milky Way, which one of these two binoculars would give me more pleasing views?

If I try Andromeda galaxy: in which one of these two will it be easier to notice something?

Or is the answer entirely subjective?




No, it's not subjective. 8x30s will show considerably more than 6x30s on each and every one of the subjects that you named. The difference will probably be biggest on the Double Cluster, because of its andundant, close-packed stars.

Quote:

I also feel kind of guilty trying to use 30-35mm bins for astronomy.




You shouldn't! Many renowned observers have said that 7x35s were their very favorite instruments of all. My favorite binoculars are my image-stabilized 10x30s.


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SMark
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Re: 7x35 binoculars for viewing the stars? new [Re: Tony Flanders]
      #5561507 - 12/08/12 09:05 PM

You can look at my collection below and know that I will be more often taking a 7x35 with me when I go out under the stars. I especially enjoy wide angle binoculars, and the 7x35 configuration typically has the widest angle choices. Wide angle 7x35 star field images can be quite breathtaking.

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David E
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Re: 7x35 binoculars for viewing the stars? new [Re: mv1612]
      #5561520 - 12/08/12 09:14 PM

Quote:


I think I will still buy the 6x Yosemite. The exit pupil on the 8x is too small if it is to be used for the night sky, I think. I will take a decision as soon as possible...

Thanks for your help, it was invaluable.

Virgil.




I like my 6x Yosemite. I'm really impressed with the color accuracy. It has some whoppin' field curvature, but with some creative focusing and positioning of the brightest stars in the star field, you can get some really nice views. Having used the 6x so much I'm tempted to get and try the 8x version. No, the exit pupil will not be too small for astro-work; I use my 12x36 Canon IS binocs (3mm exit pupil) for astro use all the time.


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mv1612
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Reged: 08/11/09

Re: 7x35 binoculars for viewing the stars? new [Re: David E]
      #5561642 - 12/08/12 10:54 PM

Thanks. Tony, I'm encouraged that the 8x30 shows fainter stars that the 6x30, probably because of a darker background. That's important for me. So I'm leaning towards the 8x30 form factor. Now, in the meantime I've found other binoculars very similar to the Leupolds:

Leupold Yosemite 6x30 8.0deg 482g $80
Leupold Yosemite 8x30 7.4 482 $95
Celestron Nature 8x30 8.2 482 $52
Kowa YF 6x30 8.0 470 $99
Kowa YF 8x30 7.5 473 $105
Vortex Raptor 6.5x32 7.8 490 $120
Vortex Raptor 8.5x32 7.4 490 $130

Why can't I put tabs between those columns? I was trying to show the field of view, weight and price.

All seem to be Bak4 (please correct me if not). Some of them could be clones of another... The Kowa seems to be identical to the Leupold... The Celestron is intriguing, only $55... Probably corners have been cut somewhere, if it's not in the optics I might be tempted. On the other hand, if the Leupolds and Kowas are significantly better than the Celestron, then I'm ready to pay their price. Nice to have alternatives. I try not to fall into "paralysis by analysis", but the reality is that I'm in no rush, it will not be a present for Christmas. Did anyone compare some of these? Thanks...


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Plan9
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Re: 7x35 binoculars for viewing the stars? new [Re: Tony Flanders]
      #5561647 - 12/08/12 10:57 PM

Quote:

Star colors are generally more saturated in larger apertures. So 10x50s show more colorful stars than 10x30s. That's a function of aperture, not exit pupil.




Tony,

The discussions I've seen about this here state that exit pupil determines brightness (so the same exit pupil for any aperture looks equivalent in brightness, although the limiting magnitude will go up with more aperture). Color perception is related to brightness (cone cells are less sensitive - need more flux), so wouldn't it actually be true that exit pupil determines color perception?

You are right, though, in the sense that you will see more stars in the 10x50 than the 10x30, therefore more of the stars that are colorful.

Bill


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mv1612
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Re: 7x35 binoculars for viewing the stars? new [Re: mv1612]
      #5561648 - 12/08/12 10:58 PM

"The whoppin' field curvature" of the 6x30 pushes me also towards the 8x30... Thanks David.

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