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bino/quadroculars?

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#101 PeterDob

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Posted 06 September 2017 - 11:00 AM

If only that were true...... I am still trying to fathom how the resolution of a visually used binoscope with one eye looking into each eyepiece can be any more than that of each of the scopes on their own....

 

 

Like I said, if we were talking about a binoscope that transmitted the images of both mirrors into a single eyepiece, you would accept this immediately. Don't ask me how but observing e.g. close double stars or planets with one eye closed or with both eyes through a binoscope is a completely different thing. I guess it has something to do with both eyes having a better resolution than only one (e.g. like reading a text from a distance)... I don't know, but it's true.

 

 

Given the wide variation in subject brightness, size and form, it's probably foolhardy to try and pin things down to one value. But if one has to do so in order to give *some* idea, being a bit on the conservative side has merit.

 

Yes, I agree. But too conservative is also wrong and might make people believe that a binoscope (or even a pair of binoculars) isn't worth the cost and (especially) the hassle. Let's face it, if Zanewski were right, a binoscope would only capture 41% more light. Since it's generally considered that you need at least 30% more surface aperture in order to see a difference, a binoscope would be a ludicrous instrument, hardly delivering any visible benefit. And yet, when I close one eye, I observe a difference so large that it reminds me of the time that I got a 14,5" Dob iso my C8 (well, maybe that's a little exaggerated, but still...). The extra amount of light gathering power, faint little details suddenly appearing, no more need for averted vision... it's simply amazing and that's what everyone says, not just me who may sound biased. So I guess it's better that we leave those numbers for what they are and let people see for themselves. My door is always open to everyone...

 

Peter

 

PS: There's a chance that I may soon do a direct comparison with a 32" mono Dob. Now that will be a challenge! grin.gif


Edited by PeterDob, 06 September 2017 - 11:13 AM.


#102 daquad

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Posted 06 September 2017 - 03:02 PM

Dom,

Assuming a detection ratio of 1.414 (aperture equivalent of 1.189):

 

A 6" scope with binoviewer is equivalent to a 4.24" true bino. But your visual integration boosts that by factor 1.189, making for an equivalent true bino of aperture 5.04"

 

Assuming a detection ratio of 1.7 (aperture equivalent of factor 1.3):

 

A 6" scope with binoviewer is equivalent to a 4.24" true bino. But your visual integration boosts that by factor 1.3, making for an equivalent true bino of aperture 5.51".

Glenn, that is true, but before I even look into the binoviewer, the 6" instrument (with binoviewer) is inherently a 4.24" binocular scope.  Since the 1.7 detection factor (1.3 aperture) includes the 1.189 dual eye factor, my 6" scope with a binoviewer is equivalent to a 5.51" binoscope (4.24X1.3 =  5.51)  (I don't know how I got the 5.2" number, but thanks for the correction.)

 

But even using the Campbell and Green detection factor, my 6" monocular scope should still go deeper than the 5.5" binoscope, the difference being only 5log(6/5.5) = 0.189 magnitude, hardly noticeable to the casual observer, but still in favor of the 6" monoscope in terms of detection threshold and resolution.

 

It's worth noting that the aperture ratio of the physical scopes is 6/4.24 = 1.415 and the area ratio is 2.  

 

Pete's original example compared an 18" binocular scope to a 25" monoscope.  Aperture ratio 1.39 (nearly 1.41) and area ratio 1.93 (nearly 2).  Since these scale nearly the same as my example, I don't see how the 18" binocular scope can go deeper than the 25" monoscope, for if I apply the Campbell and Green data to the 18" I get an equivalent 23.4" monoscope.   Yet Pete's experience is that the 18" binocular scope has an obviously deeper detection threshold than a 25" monoscope.

 

Seems like something else is going on that I cannot fathom with my limited knowledge of physical optics or even using the data that Pete has cited to reinforce his assertion.  What's going on?

 

Dom Q.


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#103 GlennLeDrew

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Posted 06 September 2017 - 06:41 PM

One thing to bear in mind, as I laid out in an earlier post, is this. When comparing views involving the detecting of objects/structure in a bino versus not seeing such in a monoscope, the seeming disparity in performance can become almost arbitrarily large.

 

A 10X50 bino might just reveal the California nebula (a ~2 degree long nebula which at 10X appears to be 20 degrees in length) while a 16" monoscope may not. Do we say a 2" bino is equivalent to a 16" monoscope?

 

This matter of glimpsing subtle stuff in a bino which even a considerably larger monoscope cannot quite reveal naturally leads to the impression of herculean performance by the bino. But this is not a fair comparison by which to rank capability.

 

A large object which subtends sufficient size to be well enough resolved at low power with a small aperture is already just about detected as well as can be. A larger aperture (at the same exit pupil) merely makes the object larger and reveals smaller structural detail (if present); it does not alter the actual surface brightness. When just below the threshold of detection for just one eye, two eyes bring it into sure enough visibility to make for a positive sighting. A relatively small bino might do this, whereas no amount of aperture can do so for just one eye. In such case one would not be exaggerrating too horribly as to characterize the aperture ratio as approaching 'infinity', given the detection rate of 1 (or 0.7, or even 0.1) for the bino vs zero for the monoscope.



#104 daquad

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Posted 06 September 2017 - 06:53 PM

One thing to bear in mind, as I laid out in an earlier post, is this. When comparing views involving the detecting of objects/structure in a bino versus not seeing such in a monoscope, the seeming disparity in performance can become almost arbitrarily large.

 

A 10X50 bino might just reveal the California nebula (a ~2 degree long nebula which at 10X appears to be 20 degrees in length) while a 16" monoscope may not. Do we say a 2" bino is equivalent to a 16" monoscope?

 

This matter of glimpsing subtle stuff in a bino which even a considerably larger monoscope cannot quite reveal naturally leads to the impression of herculean performance by the bino. But this is not a fair comparison by which to rank capability.

 

A large object which subtends sufficient size to be well enough resolved at low power with a small aperture is already just about detected as well as can be. A larger aperture (at the same exit pupil) merely makes the object larger and reveals smaller structural detail (if present); it does not alter the actual surface brightness. When just below the threshold of detection for just one eye, two eyes bring it into sure enough visibility to make for a positive sighting. A relatively small bino might do this, whereas no amount of aperture can do so for just one eye. In such case one would not be exaggerrating too horribly as to characterize the aperture ratio as approaching 'infinity', given the detection rate of 1 (or 0.7, or even 0.1) for the bino vs zero for the monoscope.

But we are talking about 18" and 25 " scopes, neither of which we can describe as wide field instruments.  Pete's experience contradicts the Campbell & Green EMPIRICAL data (which Pete cites to prove his claim), which says an 18" binoscope should equal a 23.4" monoscope.  Yet Pete says the 18" binoscope outperforms a 25" monoscope with respect to detection threshold and even resolution.  Something is amiss.



#105 GlennLeDrew

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Posted 07 September 2017 - 12:23 AM

Dom,

It's not a requirement that an instrument qualify as wide field. The same argument would apply for a 10 arcminute nebula, which at 50X would subtend an apparent 8 degrees. If this instrument is a bino, and that nebula is just barely detectible, for a monoscope that's, say, 4X larger and hence operating at 200X (same exit pupil), the 10' nebula subtends about 33 degrees. But if the one-eyed view is just a bit too noisy to permit a glimpse, do we say the bino is as good or better than a monoscope having 4X larger aperture? To some folks, perhaps so. But I don't because we are comparing essentially a 1 (detection) and a zero (non detection), for which the ratio is effectively infinite.

 

Impressions can be dangerously misleading, and so quantifiable data are necessary. I can accept that under certain conditions, as dictated by the contrast and form of the target, binocular detections will exceed the 1.41 ratio. One study supports a detection ratio of 1.7, which implies an aperture equivalence of SQRT(1.7) = 1.3. In other words, bino/mono equivalences--if we are to insist on such--would be 100mm/130mm, 10"/13", 20"/26", and so on.

 

Based on my own observations, a detection ratio of 2, or an aperture ratio of 1.41, would be pushing things, as I recall no instance of such a notable gain. Unless we get awfully near that threshold between detecting and not detecting. But again, if we admit such a criterion, we can indeed say a handheld bino can best a huge light bucket monoscope.

 

In the end, I prefer to not dwell and fuss over an exact limit because of the differing nature of our targets. For me, it suffices to grasp a characteristic performance gain in order to put performance into perspective, and the value of root two seems to accord well enough in most instances. The fact of the visceral improvement afforded by two-eyed viewing has already sold me most thoroughly; I don't at all need to know what kind of aperture equivalence I might be experiencing. I kind of got dragged into the numbers game some years ago because of others wanting to assign a figure. ;)


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#106 PETER DREW

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Posted 07 September 2017 - 03:54 AM

Dom,

It's not a requirement that an instrument qualify as wide field. The same argument would apply for a 10 arcminute nebula, which at 50X would subtend an apparent 8 degrees. If this instrument is a bino, and that nebula is just barely detectible, for a monoscope that's, say, 4X larger and hence operating at 200X (same exit pupil), the 10' nebula subtends about 33 degrees. But if the one-eyed view is just a bit too noisy to permit a glimpse, do we say the bino is as good or better than a monoscope having 4X larger aperture? To some folks, perhaps so. But I don't because we are comparing essentially a 1 (detection) and a zero (non detection), for which the ratio is effectively infinite.

 

Impressions can be dangerously misleading, and so quantifiable data are necessary. I can accept that under certain conditions, as dictated by the contrast and form of the target, binocular detections will exceed the 1.41 ratio. One study supports a detection ratio of 1.7, which implies an aperture equivalence of SQRT(1.7) = 1.3. In other words, bino/mono equivalences--if we are to insist on such--would be 100mm/130mm, 10"/13", 20"/26", and so on.

 

Based on my own observations, a detection ratio of 2, or an aperture ratio of 1.41, would be pushing things, as I recall no instance of such a notable gain. Unless we get awfully near that threshold between detecting and not detecting. But again, if we admit such a criterion, we can indeed say a handheld bino can best a huge light bucket monoscope.

 

In the end, I prefer to not dwell and fuss over an exact limit because of the differing nature of our targets. For me, it suffices to grasp a characteristic performance gain in order to put performance into perspective, and the value of root two seems to accord well enough in most instances. The fact of the visceral improvement afforded by two-eyed viewing has already sold me most thoroughly; I don't at all need to know what kind of aperture equivalence I might be experiencing. I kind of got dragged into the numbers game some years ago because of others wanting to assign a figure. wink.gif

For me, this post eloquently sums up the discussion. On all other aspects surely it's time to agree to disagree and movve on and enjoy whatever viewing appeals.  smile.gif



#107 Fomalhaut

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Posted 07 September 2017 - 07:02 AM

PeterDob,

And IMHO, Zarenski's sqrt(sqrt 2) = ~1.19 -formula is proven dead.

This topic obviously is more complex than such a simple formula could successfully quantify.

Notice: By now, the cited test results make me even consider the other (obviously better) sqrt2-formula to deliver just approximate predictions.

Chris

Edited by Fomalhaut, 07 September 2017 - 09:29 AM.


#108 daquad

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Posted 07 September 2017 - 08:51 AM

 

Dom,

It's not a requirement that an instrument qualify as wide field. The same argument would apply for a 10 arcminute nebula, which at 50X would subtend an apparent 8 degrees. If this instrument is a bino, and that nebula is just barely detectible, for a monoscope that's, say, 4X larger and hence operating at 200X (same exit pupil), the 10' nebula subtends about 33 degrees. But if the one-eyed view is just a bit too noisy to permit a glimpse, do we say the bino is as good or better than a monoscope having 4X larger aperture? To some folks, perhaps so. But I don't because we are comparing essentially a 1 (detection) and a zero (non detection), for which the ratio is effectively infinite.

 

Impressions can be dangerously misleading, and so quantifiable data are necessary. I can accept that under certain conditions, as dictated by the contrast and form of the target, binocular detections will exceed the 1.41 ratio. One study supports a detection ratio of 1.7, which implies an aperture equivalence of SQRT(1.7) = 1.3. In other words, bino/mono equivalences--if we are to insist on such--would be 100mm/130mm, 10"/13", 20"/26", and so on.

 

Based on my own observations, a detection ratio of 2, or an aperture ratio of 1.41, would be pushing things, as I recall no instance of such a notable gain. Unless we get awfully near that threshold between detecting and not detecting. But again, if we admit such a criterion, we can indeed say a handheld bino can best a huge light bucket monoscope.

 

In the end, I prefer to not dwell and fuss over an exact limit because of the differing nature of our targets. For me, it suffices to grasp a characteristic performance gain in order to put performance into perspective, and the value of root two seems to accord well enough in most instances. The fact of the visceral improvement afforded by two-eyed viewing has already sold me most thoroughly; I don't at all need to know what kind of aperture equivalence I might be experiencing. I kind of got dragged into the numbers game some years ago because of others wanting to assign a figure. wink.gif

For me, this post eloquently sums up the discussion. On all other aspects surely it's time to agree to disagree and movve on and enjoy whatever viewing appeals.  smile.gif

 

I'm not disagreeing with Glenn.  The Campbell & Green data is empirical; it is not based on an assumed theory.  The 1.7X detection threshold is an average of the data.  And as Glenn implied, maybe a small percentage of the data even admits to a detection threshold of 2X, implying an aperture ratio of 1.414.  However this merely places Pete's 18" binocular scope as the equivalent of a 25.4" monoscope.  I don't see how Pete can say the 18" binoscope is far superior to the 25" monoscope in terms of detection threshold, for stars as well as extended objects, BTW.

 

As a final thought, it seems to me that if the 25" were used with a binoviewer, it should at least be the equivalent of the 18" binoscope.  Which instrument is easier to build and maintain?  Never mind a quadroscope.

 

Dom Q.



#109 PeterDob

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Posted 07 September 2017 - 09:38 AM

I didn't say that a 18" binoscope is "far superior" than a 25" mono. I said that: "it is at least equal, if not superior". When I used the term "far superior" I was referring to the confrontation with two 20" monos I did last year, ruling out Zanewski's approach. My binos also cost less than a 25" Obsession, but... as you hinted... it isn't an easy instrument to manage and has some serious disadvantages that don't make it suitable for everyone.

The reason why a bino - on faint, extended objects - could perform beyond the 1,41x diameter, is probably due to a much better S-N ratio. As I said, it is far less likely that a "false" light signal gets accepted as "true" by both eyes at the same time. This results in much increased contrast and probably therefore my 18" bino gave a 27" mono a really hard time.

Using a 25" with a binoviewer isn't a good idea because they all lose light due to the light path extension which will always result in vignetting. What's more, the binocular "feel" of a binoscope (or astronomical binoculars) is greater than with a binoviewer. Don't ask me why... I've used/owned just about every kind of binoviewer and in the end none of them truly satisfied me, not even the gigantic 2" Siebert which I've owned for 7 years.

Next clear night I will try to do a test between monocular vs binocular observation, which will be easy to do with my binoscope. So far I've never gone into much detail as far as this is concerned because the difference has always appeared huge, which was satisfactory enough for me. We'll see...

Peter

#110 GlennLeDrew

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Posted 07 September 2017 - 11:56 AM

PeterDob,

And IMHO, Zarenski's sqrt(sqrt 2) = ~1.19 -formula is proven dead.

This topic obviously is more complex than such a simple formula could successfully quantify.

Notice: By now, the cited test results make me even consider the other (obviously better) sqrt2-formula to deliver just approximate predictions.

Chris

The root two (1.414 factor) gain in S/N, which does in no way originate with Ed Zarenski, is hardly "proven dead", because it's based on signal theory, and does accord with observation in at least a certain regime of target morphology. As we are learning, limiting stellar magnitude determinations suggest a somewhat smaller-than-1.41 gain in detection, whereas extended source detection suggests a larger-than-1.41 gain. The characteristics of the target, be it small or large, of regular or irregular morphology, as well as the overall field brightness, would seem to determine the particular gain in detectibility by two eyes over one.


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#111 daquad

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Posted 07 September 2017 - 02:20 PM

I didn't say that a 18" binoscope is "far superior" than a 25" mono. I said that: "it is at least equal, if not superior". When I used the term "far superior" I was referring to the confrontation with two 20" monos I did last year, ruling out Zanewski's approach. My binos also cost less than a 25" Obsession, but... as you hinted... it isn't an easy instrument to manage and has some serious disadvantages that don't make it suitable for everyone.

The reason why a bino - on faint, extended objects - could perform beyond the 1,41x diameter, is probably due to a much better S-N ratio. As I said, it is far less likely that a "false" light signal gets accepted as "true" by both eyes at the same time. This results in much increased contrast and probably therefore my 18" bino gave a 27" mono a really hard time.

Using a 25" with a binoviewer isn't a good idea because they all lose light due to the light path extension which will always result in vignetting. What's more, the binocular "feel" of a binoscope (or astronomical binoculars) is greater than with a binoviewer. Don't ask me why... I've used/owned just about every kind of binoviewer and in the end none of them truly satisfied me, not even the gigantic 2" Siebert which I've owned for 7 years.

Next clear night I will try to do a test between monocular vs binocular observation, which will be easy to do with my binoscope. So far I've never gone into much detail as far as this is concerned because the difference has always appeared huge, which was satisfactory enough for me. We'll see...

Peter

Peter I am sorry for the use of the words "far superior".  I should have said "superior."  The view through a binoscope is certainly superior to that of a monoscope of the same aperture -- no argument there.  I assume when you say the difference is huge you are referring to this comparison.  However, you are also saying that the view through your 18" binoscope is equal to or superior to that of a 20" monoscope.  That I can believe.  I thought your comparison was with a 25" scope.  Sorry for the confusion on my part.

 

Dom Q.



#112 PeterDob

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Posted 07 September 2017 - 04:35 PM

Eh, Dom... what I said was that I believe my 18" binos to be at least equal to a 25" and far superior to a 20". The difference with those 20" was really big...

Peter


Edited by PeterDob, 07 September 2017 - 04:36 PM.


#113 Fomalhaut

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Posted 07 September 2017 - 05:44 PM

PeterDob,

And IMHO, Zarenski's sqrt(sqrt 2) = ~1.19 -formula is proven dead.

This topic obviously is more complex than such a simple formula could successfully quantify.

Notice: By now, the cited test results make me even consider the other (obviously better) sqrt2-formula to deliver just approximate predictions.

Chris

The root two (1.414 factor) gain in S/N, which does in no way originate with Ed Zarenski, is hardly "proven dead", because it's based on signal theory, and does accord with observation in at least a certain regime of target morphology. As we are learning, limiting stellar magnitude determinations suggest a somewhat smaller-than-1.41 gain in detection, whereas extended source detection suggests a larger-than-1.41 gain. The characteristics of the target, be it small or large, of regular or irregular morphology, as well as the overall field brightness, would seem to determine the particular gain in detectibility by two eyes over one.


Nobody said that signal theory is wrong. It just should be used in the appropriate context.
For example I'm using that law myself for calculating the gain when superimposing subs.
Two subs of similar quality contain 1.41x the information of 1 sub alone (as could also be achieved by a scope with 1.19x the aperture diameter and one single shot) ...

The mistake happens exactly when a proven law (physical or other) is used in the wrong context.
Two scopes used visually as a binocular (whithout using in-phase interference and based on above mentioned observing results) works obviously differently. Our brain seems to combine two visual pictures in its very own way...
So as for me, from now on I personally forget about the 1.19x-rule for visual and go on applying it just where it belongs, which is for AP, period.

Chris

Edited by Fomalhaut, 08 September 2017 - 03:49 AM.


#114 PeterDob

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Posted 08 September 2017 - 03:31 AM

 

Nobody said that signal theory is wrong. It just should be used in the appropriate context.
For example I'm using that law myself for calculating the gain when superimposing subs.
Two subs of similar quality contain 1.41x the information of 1 sub alone (as could also be achieved by a scope with 1.19x the aperture diameter and one single shot) ...

The mistake happens exactly when a proven law (physical or other) is used in the wrong context.
Two scopes used visually as a binocular (whithout using in-phase interference and based on above mentioned observing results) works obviously differently. Our brain seems to combine two visual pictures in its very own way...
So as for me, from now on I personally forget about the 1.19x-rule for visual and go on applying it just where it belongs, which is for AP, period.

Chris

 

 

Now thát makes sense! Good point, Chris.

 

I'm repeating the same thing over and over again, but if Zarenski were right, the difference between mono and bino would be the same as between a C8 and a (hypothetical) C9,5. Or next to nothing. We all know that this can't be true.

 

Peter

 

Ps: My apologies... apparently I've been writing Zarenski's name wrong all the time...blush.gif blush.gif blush.gif 


Edited by PeterDob, 08 September 2017 - 04:15 AM.


#115 GlennLeDrew

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Posted 08 September 2017 - 05:15 AM

Peter,

Again, Zarenski is not the originator of the root two gain; that derives from signal theory, which long predates him.

 

Why do you say that a root two gain is "next to nothing", while that very same ratio most certainly informs your impression of improvement in certain circumstances? To wit. If you conduct a comparison of limiting stellar magnitude at fixed exit pupil and find a gain of no better than 0.37 magnitude, you are enjoying in that regime of target morphology a linear aperture equivalence of ratio no better than root two (1.414.)

 

Remember, the ~0.3m gain reported by most observers on stellar sources most likely applies for you as well. And so if you feel that such objects as globular clusters benefit significantly from binocular vision, you must accept that a root two gain in detection rates is more than "next to nothing."

 

However. If you feel a ~0.3m gain is under-represented in your case, can you tell us just what is your own personal improvement in limiting stellar magnitude for bino vision at fixed exit pupil? I ask because I see thus far only non-quantified impressions, which in any scientific context are to be accorded low weighting.

 

I focus on stellar limiting magnitude because it's the easiest means of assessing comparative depth of penetration. And it's a valid indicator of aperture equivalence for point sources since, after all, we predict to good effect stellar magnitude limits based on aperture.


Edited by GlennLeDrew, 08 September 2017 - 05:23 AM.


#116 PeterDob

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Posted 08 September 2017 - 05:44 AM

Zarenski was the one who misinterpreted the 1,41x factor, that seems to be clear now. It would also be impossible to do an exact limiting magnitude test because humans are too easily biased and are poor at assessing which star we have seen and which we haven't. Any such test would have a poor result.

 

Therefore I prefer to stick to the "impression" that I get, how unscientific that may sound. You have to admit that a 18% linear diameter increase, as you are suggesting to be the norm between mono and bino, would result in a hardly noticeable improvement at the eyepiece. A C8 against a C9.5. Yet anyone who's ever observed with binoculars, small or large binoscopes and who's compared one against two eyes vision will tell you that that is pure nonsense and that the difference is significant, to say the least.

 

As I wrote in my article, people who'd observed Stephan’s Quintet through my binoscope, were so amazed that they ran off to their photographer friends at the other side of the observing field in order to inform them. The latter didn't want to believe at first so I had to return to Stephan’s Quintet another two times to show it to them as well. In the 20", the Quintet was faint and the faintest members were difficult to see. In the binoscope you didn't need averted vision at all... they were all just there and with structural details too. Where's the math behind this? Honestly, I don't know. I only want to show you that sometimes you have to leave the math behind and simply believe what you are seeing.


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#117 Fomalhaut

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Posted 08 September 2017 - 06:22 AM

The great German philosopher Arthur Schopenhauer (principal work: "Will and Representation") wrote:

"What the heart / will doesn't like, will not be let in by the head / mind".

IOW by our nature, the will ist the boss and the mind just the servant.

However eloquent the speech of any contrahent may be, we still tend not to really consider his arguments as long as they contradict our own intention.  Of course, this is not a reliable basis for scientific investigations... 

 

Years ago, there was an article in Sky & Telescope, basically showing that when we are just waiting long enough at the eyepiece of any given scope, then sooner or later a single photon from a certain star at the threshold of our vision will arrive causing the very momentary impression of having "glimpsed" that star. This way, the article said, it would be possible to "see" at least more than two magnitudes deeper than normally expected. As for me, I remember in my youth having been able to glimpse by naked eye stars which I at first couldn't see for a while but then yet suddenly "glimpsed". I used to record them on paper and to my joy later on could verify that I had located those stars' exact position (of a total of at least 13 of the Plejades, for example).

 

In the state of hoping to confirm our own will, we just might wait a bit longer or shorter at the eyepiece until we glimpse / don't glimpse a star at the threshold of our vision. Therefore, the only way to visually confirm/refute limiting magnitudes, would be by a statistically relevant number of unbiased (!) observers performing visual observation within a certain time interval (!)

in order to get a result of some general validity.

 

Less carefully done, our personal observations will at least reflect our personal intention to a relevant degree...

 

Chris       


Edited by Fomalhaut, 08 September 2017 - 07:52 AM.


#118 daquad

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Posted 08 September 2017 - 08:41 AM

Eh, Dom... what I said was that I believe my 18" binos to be at least equal to a 25" and far superior to a 20". The difference with those 20" was really big...

Peter

Yes, and that makes perfect sense. Given the Campbell & Green data, your 18-inchers should be the equivalent of a 23.4" mono, which is consistent with your observations.

 

Dom Q.



#119 PeterDob

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Posted 12 September 2017 - 10:33 AM

Right. After a couple of rainy days I finally had the opportunity to take the binos out again to do some serious testing. The weather gods were in my favour because transparency was high and seeing was deliciously calm. So I pointed the binos at a couple of random, close double stars in Delphinus (let the ArgoNavis make the choice) and I recorded what I saw. First I used only one eye (so regular 18" f/5 telescope) in order not to be biased, and then I observed with both eyes, at the same exit pupil. There have been doubts about a binoscope not offering a bigger resolution, but I can confirm with my hand on my heart that they are wrong. A binoscope offers a significant resolution increase. It's impossible to quantify how much, but the difference became more and more obvious as the doubles got closer. STF2696 are two more or less equal stars with a separation of only 0.5", so very close to the Raleigh limit of an 18" telescope (0.31"). With single-eyed viewing, the double merely looked like an elongated star. With both eyes I clearly saw two individual stars that seemed to be glued to one another. Therefore, assuming that an 18" bino performs like a 25" mono seems tempting, given the 25" Raleigh limit of 0.2".

 

Comparative Resolution Test.png

 

I'm also attaching a sketch I made last year of NGC604 in M33 and the spray of little stars I saw in it (please click on the image to see it in full resolution)...

 

NGC604 (binoscope).jpg

 

Cheers,

 

Peter


Edited by PeterDob, 12 September 2017 - 10:50 AM.


#120 GlennLeDrew

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Posted 12 September 2017 - 07:49 PM

Peter,

Are you saying that the image scale increased?

 

Or are you saying that the Airy disks decreased in size?

 

We can rule out an image scale increase, because I'll bet that a pair of stars simultaneously on opposite edges of the FoV would retain the identical disposition with one eye or both (provided the field stop edges are also nicely coincident.)

 

If there is a perceived brightening, this would tend to counter the resolution gain by virtue of the Airy disks 'bloating' somewhat.

 

The real way to test this is to carefully note the arrangement of the diffraction rings. Their central peak in intensity (around the circumference of the ring) is a fixed quantity that a bino cannot possibly alter. The ring dimension seen with one eye is the same as seen for both eyes.



#121 PeterDob

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Posted 13 September 2017 - 02:53 AM

Still don't want to believe, eh? grin.gif

 

No, obviously the image size doesn't change between one and two-eyed viewing with a binoscope. That's the beauty of it!

 

It's virtually impossible to quantify if and how much the airy disks changed in size because we're talking about such a tiny thing. Still I suspect that this must be the case, given that with one eye STF2696 looked "elongated" and with both eyes the two stars were perfectly resolved. The stars looked brighter, yet they were much more defined. Look at 1 Del: there was more black between both stars with two-eyed viewing! If you will accept without hesitation that two identical mirrors transmitting their images to one eyepiece will automatically increase resolution to that of a single mirror 1.41x their diameter, why not accept that more or less the same happens when those mirrors transmit their image to our brain via separate eyes? Why can't our brain function like a sort of prism that stacks the images (for an unquantifiable amount)? I've heard many people say "no" to this, because: "It's our brain" (or in other words: "I don't know why not"). Whereas my observations suggest the opposite and that, apart from a significant light gain - on which we all seem to agree by now -, there's also a significant gain in resolution.

 

Peter


Edited by PeterDob, 13 September 2017 - 02:55 AM.


#122 Fomalhaut

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Posted 13 September 2017 - 03:50 AM

 ...there's also a significant gain in resolution.

 

Hi Peter,

 

I would rather call it "a significant gain in perceived resolution", because our brain just uses our eyes as photon-collecting sensors. However, as everybody knows, it's not the eyes that "see"  -  it's our brain which does.

 

The size of the Airy-disk projected on the retina certainly doesn't change in either eye just because there is another eye collecting photons next door. But binocularly the brain has two independent sensors at its disposal providing more information to analyze in order to finally synthesize a better image.

 

But how exactly the brain merges and analyzes the two incoming streams of information in order to calculate a more informative image than one-eyed only, is still quite unexplored shrug.gif .

 

There still are phenomena which can't be quantified just by using simple formulas...

 

Chris


Edited by Fomalhaut, 13 September 2017 - 05:29 AM.

  • Gleb1964 likes this

#123 PeterDob

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Posted 13 September 2017 - 07:18 AM

All right. But why won't anyone answer my point, i.e. that when the two mirrors transmit their signal to one eyepiece suddenly there IS an increase in resolution, even though both mirrors have their Rayleigh limit?

Peter

#124 GlennLeDrew

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Posted 13 September 2017 - 08:02 AM

Peter,

I have never once suggested that two identical mirrors delivering their images to the same eyepiece will increase resolving power. Unless one is undertaking long baseline interferometry, where great effort is made to retain phase coherence (outside the province of at least 99.9% of amateurs), with the resolution gain even there being restricted to one axis only, the merged images in the one eyepiece can offer zero increase in resolving power.

 

Let's repeat that: Optically merging two identical images for viewing with one eyepiece realizes no increase in resolving power.

 

Furthermore, the root two gain of 1.414 in resolving power *that originates entirely in the brain* equates to an equivalent *areal* increase of 1.414, which is a *diametrical* increase of 1.189.

 

A *linear* equivalent aperture of 1.414 derives from a *doubling* of area, which would attend a doubling in the detection rate. But we see the higher figures here being not 2, but instead around 1.7, meaning a linear aperture equivalent of 1.3.

 

In any event, for 'brighter' objects like stars, it's likely a root two (1.41) detection ratio for bino vision is nearer to reality than is 1.7.

 

Bottom line. A binocular in no way by itself causes a resolution increase. It's physically impossible. Whatever gains accrue occur entirely in our visual cortex. And that derives purely from the improvement in signal to noise.

 

If first with one eye you are presented with a given scene, then with the other eye you see essentially the same thing, just because you now open both eyes does not by some magic cause the optics to operate in any way whatsoever differently. Each eye is still receiving the same image as does each when used alone. As you read this screen the exact same principles apply. How your eyes and brain operate when processing the array of pixels before you is precisely like the use of an instrument. Try alternately looking with one eye alone, then comparing to the two-eyed view. You will realize the identical gains as obtained from an optical instrument (discounting differences in scene brightness as compared to astro observing ;) ). That's because in the end it's *only* about your eyes and brain. The optics in no way alter this fundamental phenomenon.



#125 PeterDob

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Posted 13 September 2017 - 08:42 AM

Thus... with your reasoning... if you combine two 18" mirrors with a precision greater than 1/4 lambda, they will deliver the resolution of a 25", right?

Peter


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