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bino/quadroculars?

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#76 Jon Isaacs

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Posted 04 September 2017 - 11:23 AM

Exactly, Jon! An even better test would be to measure the airy disk in a binocular system. This will confirm a linear aperture increase of 1,41x, as theory predicts.

Peter

 

A binocular telescope that consists of two telescopes with two separate sensors, (human eyes) has the same resolving power as the single objectives that make up the pair.  You can't beat diffraction. 

 

Jon



#77 GlennLeDrew

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Posted 04 September 2017 - 12:03 PM

Jon,

Indeed, the instrument does have its inherent resolving power. But how we see that image is another aspect. Whether the exit pupil is large or tiny, and so the image is crisp or fuzzy, with two eyes we discern more than we can than with one. A 120mm refractor or bino both resolve to 1". That's indisputable. The bino does not somehow permit to resolve to 0.84". It's just that whatever is presented by the bino is more definitely seen due to reduced noise.

 

Now, when the exit pupil is large enough to have diffraction not resolved, our visual system effectively is undersampling the image. We see a crisp view that can bear more magnification and thereby reveal more detail. In this context a binocular *does* afford a real gain in resolving power.

 

But when diffraction has become resolved, a binocular merely reveals a more definite view of an already blurred image. However, once again, at sufficiently low brightness and/or contrast, where our now poorly resolving visual system does not discern detail at the level of diffraction, very real gains in resolution attend via a binocular.


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#78 GlennLeDrew

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Posted 04 September 2017 - 12:07 PM

https://www.research...r_Visual_Acuity

 

As I said, I'm no technical expert. But the above-mentioned study seems to be the most comprehensive ever done on this subject. If you like, I can find a couple of others for you.

 

Peter

I've requested the paper, and await its arrival in my email inbox. The abstract describes an interesting method employed. Numerous papers I've read over the years included a brief word on the conclusion; that would've been handy here. ;)



#79 PeterDob

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Posted 04 September 2017 - 12:50 PM

A 120mm refractor or bino both resolve to 1". That's indisputable. The bino does not somehow permit to resolve to 0.84".

 

Eh... yes it does. When we talk about aperture, we find it only logical that the bigger the aperture, the greater the resolving power. Why shouldn't that also apply to binoscopes which in every effect offer twice the amount of aperture? In fact, why would NASA go through all the trouble of building multiple telescopes (even several optical telescopes linked to each other) if there wouldn't be any gain in resolution? That simply doesn't make sense! Why would anyone still want a binoscope if there weren't any real gains (or marginal ones)?

 

A binoscope behaves exactly as a telescope of twice the aperture and the S-N ratio is only a bonus.

 

Peter



#80 junomike

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Posted 04 September 2017 - 01:30 PM

 

A 120mm refractor or bino both resolve to 1". That's indisputable. The bino does not somehow permit to resolve to 0.84".

 

Eh... yes it does. When we talk about aperture, we find it only logical that the bigger the aperture, the greater the resolving power. Why shouldn't that also apply to binoscopes which in every effect offer twice the amount of aperture? In fact, why would NASA go through all the trouble of building multiple telescopes (even several optical telescopes linked to each other) if there wouldn't be any gain in resolution? That simply doesn't make sense! Why would anyone still want a binoscope if there weren't any real gains (or marginal ones)?

 

A binoscope behaves exactly as a telescope of twice the aperture and the S-N ratio is only a bonus.

 

Peter

 

I'm no optical expert but this doesn't jive with my findings.

In direct comparison to my APM 100's (Binoscope) I found it almost identical to a friends TEC 140 using BV's for limiting magnitude.

However, using an 8" SCT in mono-mode easily destroys the Binoscope for limiting magnitude.

IME what two eye's see in a  4" scope (2) is not even close to what one eye sees in an 8" telescope.


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#81 Jon Isaacs

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Posted 04 September 2017 - 02:15 PM

 

A 120mm refractor or bino both resolve to 1". That's indisputable. The bino does not somehow permit to resolve to 0.84".

 

Eh... yes it does. When we talk about aperture, we find it only logical that the bigger the aperture, the greater the resolving power. Why shouldn't that also apply to binoscopes which in every effect offer twice the amount of aperture? In fact, why would NASA go through all the trouble of building multiple telescopes (even several optical telescopes linked to each other) if there wouldn't be any gain in resolution? That simply doesn't make sense! Why would anyone still want a binoscope if there weren't any real gains (or marginal ones)?

 

A binoscope behaves exactly as a telescope of twice the aperture and the S-N ratio is only a bonus.

 

Peter

 

 

Peter:

 

A binocular telescope does not behave exactly as telescope of twice the aperture.  If it were a twin objective telescope or segmented mirror  telescope like the Kecks, where objective or mirror contributes to the overall aperture then it would perform according to the combined aperture.

 

But a binocular telescope does work that way, it's two separate objectives that are not linked.  It produces a pair of identical Airy disks, one in each eye and the eye has no way of combining them to reduce their size.  

 

Jon


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#82 daquad

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Posted 04 September 2017 - 02:36 PM

 

 

A 120mm refractor or bino both resolve to 1". That's indisputable. The bino does not somehow permit to resolve to 0.84".

 

Eh... yes it does. When we talk about aperture, we find it only logical that the bigger the aperture, the greater the resolving power. Why shouldn't that also apply to binoscopes which in every effect offer twice the amount of aperture? In fact, why would NASA go through all the trouble of building multiple telescopes (even several optical telescopes linked to each other) if there wouldn't be any gain in resolution? That simply doesn't make sense! Why would anyone still want a binoscope if there weren't any real gains (or marginal ones)?

 

A binoscope behaves exactly as a telescope of twice the aperture and the S-N ratio is only a bonus.

 

Peter

 

 

Peter:

 

A binocular telescope does not behave exactly as telescope of twice the aperture.  If it were a twin objective telescope or segmented mirror  telescope like the Kecks, where objective or mirror contributes to the overall aperture then it would perform according to the combined aperture.

 

But a binocular telescope does work that way, it's two separate objectives that are not linked.  It produces a pair of identical Airy disks, one in each eye and the eye has no way of combining them to reduce their size.  

 

Jon

 

Jon, I know you meant ..." a binocular telescope does not work that way."  And to be clear Peter, a binocular telescope would produce twice the resolution (and only along a line joining the two objectives) only if the two separate images could be combined in phase.  Then the increased resolution could be observed with only one eye and would occur only in a line that is parallel to the line joining the centers of the two objectives.

 

Dom Q.


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#83 PeterDob

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Posted 04 September 2017 - 02:42 PM

You can do a simple test to demonstrate that resolution's greatly enhanced by binocular viewing. Try to read a distant text with one and both eyes.

 

Here's an interesting thread on binocular resolution:

 

www.cloudynights.com/topic/3831-resolution-of-binoculars

 

And here's a comprehensive list of all scientific studies concerning binocular summation. They all confirm 1,41x so Zanewski's quite alone...

 

Bartels, M. 2012. Visual astronomy. (http://www.bbastrode...com/visual.html).

 

Campbell, F.W., and Green, D.G. 1965. Monocular versus binocular visual acuity. Nature 208: 191.

 

Harrington, P. 2011. Cosmic Challenges, Cambridge University Pres. p. 5

 

Meese, T.S., Georgeson, M.A., and Baker, D.H. 2006. Binocular contrast vision at and above
threshold. Journal of Vision 6: 1224.

 

Pirenne, M.H. Binocular and Uniocular Threshold of Vision. 1943. Nature 152: 698.



#84 GlennLeDrew

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Posted 04 September 2017 - 03:03 PM

As noted, a binocular provides two images having the same sized Fresnel pattern of diffraction. The synthesis of these images in our visual cortex cannot alter this. It's easy to prove. Pop into your binoscope an eyepiece pair delivering, say, a 0.7mm exit pupil, so as to resolve the Airy disk and (hopefully) one or two rings. Look with one eye, then both. The diffraction pattern remains unchanged in scale.

 

The boosting of resolution via long baseline interferometry is a whole other matter, and utiluzes the *separation* of the objectives in conjunction with phase coherence to realize a one-dimensional resolution increase along the axis connecting the two instruments.


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#85 daquad

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Posted 04 September 2017 - 03:16 PM

You can do a simple test to demonstrate that resolution's greatly enhanced by binocular viewing. Try to read a distant text with one and both eyes.

 

Here's an interesting thread on binocular resolution:

 

www.cloudynights.com/topic/3831-resolution-of-binoculars

 

And here's a comprehensive list of all scientific studies concerning binocular summation. They all confirm 1,41x so Zanewski's quite alone...

 

Bartels, M. 2012. Visual astronomy. (http://www.bbastrode...com/visual.html).

 

Campbell, F.W., and Green, D.G. 1965. Monocular versus binocular visual acuity. Nature 208: 191.

 

Harrington, P. 2011. Cosmic Challenges, Cambridge University Pres. p. 5

 

Meese, T.S., Georgeson, M.A., and Baker, D.H. 2006. Binocular contrast vision at and above
threshold. Journal of Vision 6: 1224.

 

Pirenne, M.H. Binocular and Uniocular Threshold of Vision. 1943. Nature 152: 698.

I read the two links you suggested and found nothing to refute what I said.  As GlennLeDrew pointed out, any increase in resolution using a binoscope is purely a result of using two eyes, which our brain perceives as an increase in the S/N ratio, and has nothing to do with the inherent properties of the instrument.  Binoviewing, whether a binoscope or a binoviewer on a monoscope reduces the annoyance of floaters for the same reason.

 

Dom Q.



#86 PeterDob

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Posted 04 September 2017 - 03:25 PM

That's not what the people who built the Large Binocular Telescope are saying. BTW, NASA confirms the 1,41x factor...

 

Peter



#87 Jon Isaacs

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Posted 04 September 2017 - 04:10 PM

That's not what the people who built the Large Binocular Telescope are saying. BTW, NASA confirms the 1,41x factor...

 

Peter

 

The LBT uses two mirrors and interferometry to establish a long baseline.  This is not the case with any amateur telescope.  And I think the factor along that single axis is greater than 1.41x.  

 

'nuff said.

 

Jon 



#88 GlennLeDrew

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Posted 04 September 2017 - 04:21 PM

Peter,

Are you certain as to what the 1.41 factor applies? It's signal to noise, which corresponds to the area of the equivalent aperture, not the diameter.

 

Your thesis would seem to be that two eyes double (factor 2) the signal to noise ratio, thereby resulting in an equivalent aperture of factor 1.41X. But I keep seeing from most sources the 1.41 factor for improvement in S/N, not 2.



#89 PeterDob

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Posted 04 September 2017 - 04:33 PM

No, 1,41 is the factor of linear size as confirmed by all sources except Zanewski, which seems to be the only one you quote. S-N just adds to that, as demonstrated by Meese et al. and offers binoscope performance up to 1,8x its diameter. 

 

Try to put a 100mm binocular (with changeable eyepieces to get similar mag) next to a C8 and you'll see what a hard time the latter has in trying to outperform. 

 

The same goes for resolution. Two eyes resolve better than one, just like a composite telescope resolves better than a mono, as demonstrated by the LBT. NASA states that the 8m LBT performs like a 11,2m mono on light gathering power, i.e. 1,41x linear. One brain or one CCD... it makes no difference.

 

Peter


Edited by PeterDob, 04 September 2017 - 04:35 PM.


#90 GlennLeDrew

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Posted 04 September 2017 - 06:38 PM

NASA's statement that the 8m LBT has the light grasp of an 11.2m mono scope is quite true. But they're most assuredly not suggesting this would be the result if it could be used as a visual binocular.

 

The actual light grasp of two optical systems when used as a visual binocular does NOT simply add together to make the image in one's visual cortex equal to a monoscope of the same total aperture area (and hence 1.41X larger in diameter.)

 

I think you may have misconstrued the meaning of the factor 1.41, it relating to *area*, not diameter, where aperture equivalence is concerned.

 

When comparing performance of a smaller binocular to a larger monoscope, it's *imperative* that the test be done at the same exit pupil, not the same magnification. Just as an instrument permits to see fainter stars and eak out more detail as magnification is increased (up until the exit pupil has shrunk to about 1mm), by boosting the smaller instrument's magnification you are giving it an artificial enhancement; that's cheating, if you will. What if the monoscope is already at a 1mm exit pupil? Do you push the bino to smaller than this into 'empty magnification' territory in the incorrect quest for similar magnification? For then the bino would look to be the poorer performer by virtue of pushing it too far.

 

To take this to an extreme. A monoscope is working at a 7mm exit pupil, and a bino is working at a 1mm exit pupil (its resolution limit). In terms of actual, discernible detail, the bino could have an aperture as small as 1/7 that of the monoscope for a nicely bright target. And if we take a 1mm exit pupil as permitting to see stars 2 magnitudes (a factor of 6.3) fainter than with a 7mm exit pupil, the bino aperture *area* could be about 1/6.3 that of the monoscope, which is a linear aperture ratio of SQRT(6.3), meaning the bino could have a 2.5X smaller aperture. That's the kinds of disparity in aperture that can result when seeking comparable resolution or depth of penetration on point sources where the exit pupils vary.

 

But when we compare instruments at the same exit pupil, the performance of the monoscope is equal to that of the bino when its aperture area/diameter is 1.414/1.189 that of the bino aperture.



#91 PeterDob

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Posted 05 September 2017 - 03:20 AM

No, it's you who's misinterpreted. Where does 1,41x the area actually come from? It's a figure that doesn't make sense at all since we're talking about 2x the area! Hence a binoscope DOES put both images together and you get 1,41x linear diameter, as confirmed by all scientific literature (except Zanewski for whatever reason). If we were talking about two telescopes transmitting their images to a beamsplitter and then into one eyepiece, everyone would immediately say that the aperture's doubled. But because the beamsplitter's in our brain, suddenly that becomes 1,41??? That's absurd!

 

NASA clearly states that their 8m bino performs like an 11,2m mono and they would do the same if it were used as a visual binocular instrument. Exactly like I state that an 18" bino performs like a 25" mono, both in terms of light gathering power (twice the surface) and resolution.

 

In fact, you have already admitted yourself that the airy disk of a binoscope's reduced as you state that a bino performs like a 1,18x mono. 

 

S-N has nothing to do with this. The only thing S-N does is accepting less "false" light signals, resulting in a darker background and more contrast. This is an extra bonus on top of the 1,41x linear diameter increase.  

 

EDIT: Before, you said to do the test with one eye closed and both eyes. In a binoscope the exit pupil remains the same with one or both eyes so I could easily do a test this way. That's another beautiful thing about binoscopes, i.e. that you can have the light gathering power and resolution of a telescope 1,41x its diameter but still retain the exit pupil of the much smaller instrument.

 

Peter


Edited by PeterDob, 05 September 2017 - 05:41 AM.


#92 GlennLeDrew

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Posted 05 September 2017 - 08:20 AM

No, it's you who's misinterpreted. Where does 1,41x the area actually come from? It's a figure that doesn't make sense at all since we're talking about 2x the area! Hence a binoscope DOES put both images together and you get 1,41x linear diameter, as confirmed by all scientific literature (except Zanewski for whatever reason). If we were talking about two telescopes transmitting their images to a beamsplitter and then into one eyepiece, everyone would immediately say that the aperture's doubled. But because the beamsplitter's in our brain, suddenly that becomes 1,41??? That's absurd!

 

NASA clearly states that their 8m bino performs like an 11,2m mono and they would do the same if it were used as a visual binocular instrument. Exactly like I state that an 18" bino performs like a 25" mono, both in terms of light gathering power (twice the surface) and resolution.

 

In fact, you have already admitted yourself that the airy disk of a binoscope's reduced as you state that a bino performs like a 1,18x mono. 

 

S-N has nothing to do with this. The only thing S-N does is accepting less "false" light signals, resulting in a darker background and more contrast. This is an extra bonus on top of the 1,41x linear diameter increase.  

 

EDIT: Before, you said to do the test with one eye closed and both eyes. In a binoscope the exit pupil remains the same with one or both eyes so I could easily do a test this way. That's another beautiful thing about binoscopes, i.e. that you can have the light gathering power and resolution of a telescope 1,41x its diameter but still retain the exit pupil of the much smaller instrument.

 

Peter

I never once stated that a bino alters the Airy disk. In fact, in a recent post replying to Jon I explicitly covered this by reinforcing the fact that if each half of a bino produces a Frenel pattern of given size, when used as a bino the same size Fresnel pattern obtains. The *intrinsic* resolving power is quite unchanged. It is we who derive more information due to reduced *visual system* noise. And yes, signal to noise has everything to do with it.

 

The person who enjoys the most benefit has both eyes of essentially similar performance. Assuming one uses one's 'best' eye for monoscoping, for folks who have a poorer second eye (for reasons of physical defect or processing in the visual cortex) which contributes less to the integrated image derive less benefit from a binocular. Of course the worst case scenario attends when one is blind in one eye; a binocular is then just a monocular.

 

That paper you linked to recently and which involves testing bino vision using a varying pattern on an oscilloscope screen (and which I requested--to be sent sometime by email); can you summarize the conclusion?



#93 PeterDob

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Posted 05 September 2017 - 11:24 AM

Here's the graph that shows the heart of the Campbell and Green contrast sensitivity tests:

 

Campbell and Green.png

 

The straight horizontal lines represent the average sensitivity ratio at different spatial frequencies, which is 1,41x.

 

I'd also like to add the conclusions of Meese et al. of their 2006 study on binocular contrast vision at and above threshold:

 

Quote:

 

Binocular summation ratios were calculated by dividing the monocular detection threshold by the binocular detection threshold; this gives the ratio of binocular to monocular sensitivities. (We also express these ratios in decibels by taking log 10 and multiplying by 20.) Binocular summation ratios are shown in Figure 2 for the four different stimulus durations. In all cases, summation is greater than the quadratic prediction of √2 (3 dB) but less than a perfect linear summation ratio of 2 (6 dB) and has an average of 1.70 (4.6 dB). In particular, this result is inconsistent with the quadratic summation model of Legge and the ideal linear summation model of Campbell and Green, both of which predict binocular summation ratios of √2 (3 dB). Psychometric slopes did not differ significantly between monocular and binocular testing. Mean values (±1 SE, n = 8) for slope parameter β were 3.00 ± 0.27 (monocular) and 3.31 ± 0.27 (binocular).

 

The high levels of binocular summation that we found confirm the existence of nearly linear summation of contrast across the eyes. However, careful measurement of monocular, binocular, half-binocular, and dichoptic masking functions has revealed a complexity to the functional form of early luminance contrast vision that had not previously been suspected. We have embedded this in physiologically plausible architectures containing accelerating transducers, contrast gain control, binocular summation, and late additive noise. Only the two best fitting models made good predictions for the slope of the psychometric functions. With no further fitting, these models also provided a unifying account of contrast discrimination thresholds and contrast matching between dichoptic and binocular stimuli. Features of both models are that suppression occurs within and between the eyes and that the initial monocular transduction of contrast is almost linear.

 

Unquote

 

Peter


Edited by PeterDob, 05 September 2017 - 11:28 AM.

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#94 daquad

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Posted 05 September 2017 - 03:03 PM

That's not what the people who built the Large Binocular Telescope are saying. BTW, NASA confirms the 1,41x factor...

 

Peter

I was referring only to resolving power, not detection threshold.  I would expect the LBT to combine the images from each objective in phase, for an effective collecting area of 2X and an effective aperture of 1.414X.  But, as you know, visual binocular scopes do not combine the images in phase, which begs the question:  How can a visual binoscope deliver 1.414X the detection threshold of a monoscope?  I am still mulling over the Campbell & Green conclusion that a binocular scope has on average 1.7X the sensitivity (detection threshold) as the same aperture monoscope.  I'm not sure what the diagonal plots represent in terms of contrast sensitivity, other than the fact that two eyes are better than one.  Since they use a log scale with no grid lines, it is difficult to tell by how much two eyes are better.

 

Dom Q.


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#95 GlennLeDrew

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Posted 05 September 2017 - 06:11 PM

Peter,

I still haven't received that paper, so thanks for the summary...

 

So, we see that some investigators obtain a detection boost of about root two (1.41), but here we see a result of 1.7. That latter figure would then correspond to a linear aperture ratio of SQRT(1.7) = 1.3. For example, a 130mm aperture monoscope would be about equal to a 100mm binocular--at the same exit pupil.

 

It would seem that the point source result of around 0.3-0.35 magnitude derived by numerous amateurs using stars would indicate a smaller improvement n binocular detection than that obtained by a resolved pattern of cyclical variation.

 

There might be a bit of a boost in detection when a repeating pattern is involved versus a single patch or blob. This *might* in part account for the larger-than-1.41 detection ratio.



#96 daquad

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Posted 05 September 2017 - 07:46 PM

Peter,

I still haven't received that paper, so thanks for the summary...

 

So, we see that some investigators obtain a detection boost of about root two (1.41), but here we see a result of 1.7. That latter figure would then correspond to a linear aperture ratio of SQRT(1.7) = 1.3. For example, a 130mm aperture monoscope would be about equal to a 100mm binocular--at the same exit pupil.

 

It would seem that the point source result of around 0.3-0.35 magnitude derived by numerous amateurs using stars would indicate a smaller improvement n binocular detection than that obtained by a resolved pattern of cyclical variation.

 

There might be a bit of a boost in detection when a repeating pattern is involved versus a single patch or blob. This *might* in part account for the larger-than-1.41 detection ratio.

Yeah, Glenn, that is what my first calculation was. So a 4" binoscope is the equivalent of a 5.2" monoscope.  So a 4" binooscope can go 0.57 mags deeper than a 4" monoscope.   However, I think we both agree that the resolution of the 4.2" binoscope is still that of a 4.2" monoscope.  I need to check out the detection threshold difference with my binoviewer on my 6" refractor.

 

Here is how:  With the binoviewer each eye receives one half the total light delivered by the objective. (I'm ignoring the slight losses from the beam splitter.)  Thus, each eye receives the equivalent signal from a 4.2" refractor (6X 0.7=4.2).

So in effect I have a 4.2" binoscope.  According to Campbell & Greene, my 4.2" binoscope is the equivalent of a 5.2" monoscope.  The magnitude detection difference (gain) over a 4.2" mono 5log(5.2/4.2) = 0.46 mag.  However, relative to my 6" mono scope and according to the Campbell & Greene data, there should be a net loss in faintest magnitude of 0.31: 5log(5.2/6) = -0.31.   (Here , I am assuming, that the 1.19 factor for cortex signal processing is included in the 1.7x factor.)  Yet, Pete, in his experience notes a net gain in detection threshold over that of a larger monoscope.

 

This is not an easy test to perform, because most people will have difficulty detecting a 1/3 mag difference without much experience.  However, one can look for the faintest star visible in the bino mode and compare that with the view in the mono mode or vice versa.  I would encourage all who have followed this thread to try this test or any test they think is relevant to decide the issue.  The 13th mag star near the Ring Nebula (M57) might be a good test target, for example.

 

I will also stop my 6" scope to 5.2" and compare the 5.2" monoview view with the binoviewer (4.2" bionscope).  They should be equivalent.

 

Comments are encouraged.

 

Dom Q.


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#97 GlennLeDrew

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Posted 05 September 2017 - 08:15 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".


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#98 PeterDob

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Posted 06 September 2017 - 04:39 AM

Daylight resolution tests show a detection increase up to 16% (I haven't got the link right now). But the heart of the matter is that the reality at the telescope is quite different, allowing for a much more significant increase of resolution with a binoscope.

I have asked Mr. Otte for advice and will quote his response here:

QUOTE

Let me start with Pirenne's study, which compares what you see with one vs two eyes. It appears to depend greatly on the amount/intensity of light that's being used. At a probability of 50% that you see a signal with one eye, you get a probability of 75% with both eyes. This is 1.5x more and hence the summation factor is 1.5. With a probability of 60% you get the notorious summation factor of 1.4 and with a probability of 1 (daylight) you get a summation factor of 1.

Now continue with your reasoning. The surface of your mirrors is 509 sqin. With a factor of one, that would mean a diameter of 25.4in or 1.41x linear. With a factor of 1.41 this becomes 360 or 21.3in diameter. With a factor of 1.5 this is 339 or 20.8in diameter, etc.

In short, if you assume the total surface as X and interpret the summation factor Y as just Y of the total light, the bigger the factor results in an ever smaller mono mirror, whereas during daylight you'd get a mono mirror twice as large. Let's agree that this is not the correct way to look at this.

This doesn't mean that Zarenski hasn't got a point. His reasoning is this: if the summation factor is 1.4, then you see 1.4 times more with both eyes (or mirror). So you have to multiply the surface of one mirror by 1.4, which corresponds to a diameter of 21.3, or 1.18x. This, however, does not correspond to the observations of people who observe with a big binoscope.

What seems to be the problem?

1) As I quoted in the first paragraph, there is no such thing as one and the same binocular summation factor. It largely depends on how you measure, which parameter you measure, resolution, detection etc. I've seen factors well above 2 in scientific literature.

2) There's a major confusion going on. Amateur astronomers translate the factor directly into the size of mirrors. This is something that vision scientists will never do, and with good reason too. Simply put, they look at how much better you see with both eyes compared to one. From their perspective it is total nonsense to translate this into how big that one eye would be, compared to two. We only have one eye and it doesn't get a bigger surface in order to do a comparison. In short, they completely refute the INTERPRETATION that Zarenski gives on the summation factor. Scientists would never translate the factor to how big a comparable, single surface would be. This is, understandably, an obsession of amateur astronomers. As I said, if with two 18in mirrors you don't get further than a 21.3in mono, would it still be worthwhile? Also for a telescope builder, why bother with all the fuss if a marginally larger monoscope will do?

3) It isn't clear at all whether there is a linear connection between the surface increase of a single mirror and what you'll see. Of course, if you put a camera behind it, you'll catch twice the number of photons with a mirror twice as large. But what about our brain? In Pirenne's study you see that the intensity of light doesn't have a linear curve. But no-one's doing any research about this, because vision scientists do this primarily from a medical perspective, eye abberations etc. No-one seems to be interested to know what one eye sees more with more light.

These considerations were enough for me to cast some serious doubt on the simplistic approach of "there's a summation factor of 1.4 which translates in a diameter increase if 1.18".

What I saw myself was completely different. Hence I started measuring myself. And these measurements have been confirmed over time by others (including you). It matters whether you're looking at point sources, or much fainter, extended objects such as galaxies. Everything confirms that the equivalent of two mirrors is much more than the notorious 1.18 factor. You've even quoted 27in. But which binocular summation factor would fit that??? And is this actually important???


UNQUOTE

 

I couldn't agree more. I know what I see with my instrument and I could call in many witnesses about how much more an 18" bino shows compared to a 20" mono, which according to Zarenski should be more or mess equal. I could call in the owner of the 27". I could call in Bruce Sayre or Andrea Boldrini, whose magnificent 24" binos were the inspiration for mine. This entire discussion is therefore completely useless. As I said... see where the longest queues are during a star party. That's proof enough.

Peter


Edited by PeterDob, 06 September 2017 - 05:18 AM.


#99 Kunama

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Posted 06 September 2017 - 05:34 AM

........I could call in many witnesses about how much more an 18" bino shows compared to a 20" mono, which according to Zarenski should be more or mess equal. I could call in the owner of the 27". I could call in Bruce Sayre or Andrea Boldrini, whose magnificent 24" binos were the inspiration for mine. This entire discussion is therefore completely useless. As I said... see where the longest queues are during a star party. That's proof enough.

Peter

 

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....



#100 GlennLeDrew

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Posted 06 September 2017 - 08:00 AM

Peter,

The qualitative improvement with bino observing is all I personally require to inspire me to choose a small bino over a huge monoscope. I've said this in this thread, since I joined CN in '08, and for just about the past quarter century.

 

The innate need to quantify things leads to an attempt to put the gain into numbers. Like many others, I was content to accept the simplistic root two gain based on signal theory, which was widely enough promulgated. And it closely enough accorded with my own impressions and determinations.

 

Your correspondent noted the amateur's fetishistic need to find equivalences.  How 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. For the beginner who might observe the brighter stuff, a smaller aperture equivalence would apply. Moreover, there's less chance to set up potentially unrealistic expectation. The more experienced folk who work in the realm of threshold observation can realize a larger gain and hence aperture equivalence.




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