GlennLeDrew
Postmaster
Reged: 06/18/08
Loc: Ottawa, Ontario, Canada
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Re: 12" Binocular Telescope on Refractors
[Re: edwincjones]
#5646001 - 01/27/13 12:47 PM
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A 12" bino will see stars 4X, or 1.5 magnitudes fainter than could a 6". And at given exit pupil it will reveal twice the resolving power. Just as something like a big Dob is desirable for small, dim objects, so too is a binocular. A bino is not to be considered as merely a 'small' aperture, wide field instrument. When scaled up, benefits accrue just as they do for cyclopean optik tubes.
Mono scopes are, I contend, not natural. Most of us have two eyes, and so a binocular is the 'normal' instrument. It's not that a bino affords a *gain* in signal to noise of a factor of 1.414, but rather the mono scope is a *handicap* which reduces signal to noise to a factor if 0.707.
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Joad
Wordsmith
Reged: 03/22/05
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Re: 12" Binocular Telescope on Refractors
[Re: GlennLeDrew]
#5646109 - 01/27/13 01:44 PM
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I realize, Glenn, that my trying to discuss binoculars with you is like bringing a knife to a gun fight (  , but all I know is that I am not alone in my once hoping that a 100mm interchangeable eyepiece BT could be an all-purpose astronomy instrument. It isn't. Not even close. In the very best of circumstances I can crank it up to about 85X, but the image is dim and the collimation tolerances dicey (even with my in-the-field adjustments, which my variety of Oberwerk allows for). Now, since the summation effect of two 100mm objectives is somewhere around 120mm (or, roughly, five inches), a 100mm binocular is roughly the aperture equivalent of a five inch telescope. But a good five inch refractor can easily go to over 200X. The highest any of us here on CN has gone is 150X, and that is with a special Miyauchi, and the person who owns that binocular does not often view at 150X. EdZ, with his 100mm Oberwerk, tends to stick to magnifications under 60X.
I will grant that if everything is absolutely perfect, mechanically and optically, with a binocular, in theory it should perform right up there with a telescope, but I've never seen that actually accomplished. Maybe the half million dollar monster will be the exception. I hope we find out some day.
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Tamiji Homma
Carpal Tunnel
Reged: 02/24/07
Loc: California, USA
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Re: 12" Binocular Telescope on Refractors
[Re: Rich V.]
#5646138 - 01/27/13 02:09 PM
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I am wondering if the giant binoscope goes to this location?
If it were true, it must be one of those life altering experiences in various ways.
Savio Fong's post
5100m observatory
Tammy
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Andresin150
Pooh-Bah
Reged: 08/14/07
Loc: Bogotá - La Calera / Colombia
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Re: 12" Binocular Telescope on Refractors
[Re: Joad]
#5646177 - 01/27/13 02:35 PM
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I think what Joad wants is not only possible but already exists.. The problem: cost. But for example a Bt out of a couple 102 Taks (or bigger) and a Matsumoto mirror setup will probably take you there.
But I'm not ready to go there, for me, just like the 12" Bt, this is telescope (high mag) realm. Binoculars, regardles of size, are different in their relatively small size for the aperture, big TFov for the magnification, correct image suitable for terrestrial use or simply to make them more user friendly..., the use of two eyes (and its obvious advantages) is a feature, but not exclusive of binoculars, same as portability...
So, if I wanted high magnification images, for example for planetary observation, those 12" could be a great instrument and should be considered by anyone that could afford them, but if those where mine, those would get to be used like a telescope, just like one that happens to be able to be used with both eyes...., but never like a binocular
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Mark9473
Postmaster
Reged: 07/21/05
Loc: 51°N 4°E
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Re: 12" Binocular Telescope on Refractors
[Re: Andresin150]
#5646258 - 01/27/13 03:22 PM
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I think you're right Tammy!
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Jawaid I. Abbasi
Carpal Tunnel
Reged: 06/19/07
Loc: LEVITTOWN, PA
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Re: 12" Binocular Telescope on Refractors
[Re: edwincjones]
#5646416 - 01/27/13 04:44 PM
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http://www.stathis-firstlight.de/atm/joerg_28bino.htm
Check this out
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GlennLeDrew
Postmaster
Reged: 06/18/08
Loc: Ottawa, Ontario, Canada
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Re: 12" Binocular Telescope on Refractors
[Re: Jawaid I. Abbasi]
#5646613 - 01/27/13 06:24 PM
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Commercial binos, with all the inexpensive optical elements within, can hardly be expected to perform in what for the aperture is the higher magnification regime. An instrument which will 'do it all' can be easily had, and for much less than a half mil. A couple of 5" APOs and the Matsumoto EMS system is one ready solution.
The 5" f/5 achro bino I built for a friend years ago--principally for DSO observation--worked pretty well up to ~130X (1mm exit pupil). The limiter was the chromatic aberration inherent in such an objective, followed by the 1/3 wave spherical aberration also inherent. The three mirrors in each side, being in the 1/10 wave regime, did no harm. Better objectives would have made for a decent enough planetary instrument.
And collimation was never a concern, for a quick twist of a little knob restored it in seconds.
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GamesForOne
sage
Reged: 09/29/09
Loc: Knoxville, TN
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Re: 12" Binocular Telescope on Refractors
[Re: GlennLeDrew]
#5646943 - 01/27/13 09:02 PM
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Well, with the instrument in question one should be able to put a binoviewer on one tube of the instrument and push to high power. I imagine the objectives are APO-quality and the rear can be fitted with a standard diagonal.
So the instrument likely provides both binocular vision and high magnification capabilities.
There is no reason a 100mm binocular telescope could not be operated the same way if it was designed appropriately. The limitation is cost. There is no reason the two have to be exclusive.
---
Michael Mc
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edwincjones
Close Enough
Reged: 04/10/04
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Re: 12" Binocular Telescope on Refractors
[Re: GamesForOne]
#5647548 - 01/28/13 08:07 AM
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may be a good time to reintroduce the JMI Reverse BTs.
they go up to 16" but have not been very popular here
I have never used one,
am concerned that they are hard to adjust/use
buy once considered one (briefly ) of the larger ones instead of a big dob (16" bt vs 24" dob) due to avoiding a ladder (that I would most likely fall )
not the same, but from a practical money issue, much cheaper
edj
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Mr. Bill
Postmaster
Reged: 02/09/05
Loc: Northeastern Cal
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Re: 12" Binocular Telescope on Refractors
[Re: edwincjones]
#5648354 - 01/28/13 02:30 PM
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Interesting discussion...
My own thought is that a big dob + binoviewer is the best practical solution. Big aperture binos in the 12 inch and up range are unwieldy and require a permanent location (or lots of time to assemble/disassemble.)
I have looked through a 20 incher at GSSP and while enjoying the views I was just as impressed with views through a big dob+BVs.
Edited by Mr. Bill (01/28/13 03:35 PM)
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faackanders2
Pooh-Bah
Reged: 03/28/11
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Re: 12" Binocular Telescope on Refractors
[Re: Mr. Bill]
#5649257 - 01/28/13 09:01 PM
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Large Dob and binoviewers offers option to use single eyepiece for fainter and wider objects.
Binocular offers advantage of much wider views, but are limited to lower power for reasons I don't understans (prisms?, brain merging images, etc). JMI reverse binos I would think would not be limited to higher powers.
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CuriousOne
member
Reged: 01/22/13
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Re: 12" Binocular Telescope on Refractors
[Re: faackanders2]
#5649775 - 01/29/13 07:08 AM
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The military has another type of "binoculars", I don't know how exactly they are named, but their input lens have distance about 2 meters between each other. While the specimen I've tested had only maybe 8x magnification, it was providing amazing 3d effect, when even distant mountains weren't flat any more, and you can clearly see which one is closer and which one is on the back.
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planetmalc
super member
Reged: 10/21/09
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Re: 12" Binocular Telescope on Refractors
[Re: CuriousOne]
#5650147 - 01/29/13 11:55 AM
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Having lugged 5" binoculars out to the back yard for donkey's years, I'm firmly of the opinion that a pair of 6", ideally built with light weight in mind, is the limiting aperture UNLESS you plan to leave the thing outside. If you want one-man portability AND more light grasp then it has to be commercial or home-built JMI-style reflectors, or a 'scope + binoviewer (a Dob if you must have low powers or an SCT if you like high mag). You couldn't GIVE me that 12", unless it came already installed in a decent observatory, in a property with great skies. Anything less would be a waste.
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KennyJ
The British Flash
Reged: 04/27/03
Loc: Lancashire UK
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Re: 12" Binocular Telescope on Refractors
[Re: CuriousOne]
#5650154 - 01/29/13 12:00 PM
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Fackanders,
The reason conventional binoculars tend to be relatively restricted magnification-wise as compared with Binoviewing is nothing to do with prisms or the human eyes.
It is simply because TRUE COLLIMATION is absolutely necessary, and can be tricky to achieve and maintain at magnifications in excess of around 50x.
Kenny
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ThomasM
sage
Reged: 04/19/09
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Re: 12" Binocular Telescope on Refractors
[Re: planetmalc]
#5660551 - 02/03/13 06:38 PM
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Quote:
Having lugged 5" binoculars out to the back yard for donkey's years, I'm firmly of the opinion that a pair of 6", ideally built with light weight in mind, is the limiting aperture UNLESS you plan to leave the thing outside. If you want one-man portability AND more light grasp then it has to be commercial or home-built JMI-style reflectors, or a 'scope + binoviewer (a Dob if you must have low powers or an SCT if you like high mag). You couldn't GIVE me that 12", unless it came already installed in a decent observatory, in a property with great skies. Anything less would be a waste.
I agree, if you don't live under a dark sky a 6" instrument is an excellent choice. I built such an instrument
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3720212/page...
with 160 mm f/6.5 oilpaced apo lenses, total weight 11.8 kg. Such an instrument can easily be transported to a dark side and hooked up to a mount. The big advantage compared to a bigger refractor with binoviewer, the large field, with 17 mm Ethos I get 1.6 degree TFOV at 65x maginification.
Thomas
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GlennLeDrew
Postmaster
Reged: 06/18/08
Loc: Ottawa, Ontario, Canada
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Re: 12" Binocular Telescope on Refractors
[Re: ThomasM]
#5661211 - 02/04/13 07:11 AM
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Kenny,
Dangerous to make such a blanket statement that about 50x is the limit for binoculars due to collomation constraints! The *first* bino I ever made was a 5 incher. The collimation adjustment built in posed no problem whatsoever at 130X, and could have proved eminently practicable at twice that power, if the optics allowed.
The all too common misconception that magnification somehow invalidates good engineering drives me more than a little barmy. 
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faackanders2
Pooh-Bah
Reged: 03/28/11
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Re: 12" Binocular Telescope on Refractors
[Re: ThomasM]
#5661525 - 02/04/13 11:01 AM
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Quote:
Quote:
Having lugged 5" binoculars out to the back yard for donkey's years, I'm firmly of the opinion that a pair of 6", ideally built with light weight in mind, is the limiting aperture UNLESS you plan to leave the thing outside. If you want one-man portability AND more light grasp then it has to be commercial or home-built JMI-style reflectors, or a 'scope + binoviewer (a Dob if you must have low powers or an SCT if you like high mag). You couldn't GIVE me that 12", unless it came already installed in a decent observatory, in a property with great skies. Anything less would be a waste.
I agree, if you don't live under a dark sky a 6" instrument is an excellent choice. I built such an instrument
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3720212/page...
with 160 mm f/6.5 oilpaced apo lenses, total weight 11.8 kg. Such an instrument can easily be transported to a dark side and hooked up to a mount. The big advantage compared to a bigger refractor with binoviewer, the large field, with 17 mm Ethos I get 1.6 degree TFOV at 65x maginification.
Thomas
Thomas how much did your 6" bino telescopes cost to make?
Ken
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Rich V.
Post Laureate
Reged: 01/02/05
Loc: Lake Tahoe area, Nevada, USA
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Re: 12" Binocular Telescope on Refractors
[Re: GlennLeDrew]
#5661539 - 02/04/13 11:08 AM
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I agree; with a properly designed and built bino, retaining collimation even at relatively high magnification shouldn't be a problem.
I've been transporting my Miyauchis on dirt roads in the back of a truck for years now and collimation has stayed unchanged even at 150x which is the shortest eyepiece set I have to view with. The robust mechanical design of the main prism and turret assys seems pretty bulletproof to me.
Good mechanical design and execution is necessary, though. Many commercially produced binos made to a price point may not make the cut! 
Rich
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KennyJ
The British Flash
Reged: 04/27/03
Loc: Lancashire UK
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Re: 12" Binocular Telescope on Refractors
[Re: Rich V.]
#5661663 - 02/04/13 12:27 PM
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Glen and Rich,
I never said collimation was IMPOSSIBLE with binoculars at magnifications above 50x, I just stated that it CAN be TRICKY.
There's certainly nothing "dangerous" about that statement whatsoever.
I'm surprised at you two not paying more attention to detail ! :-)
Kenny
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Rich V.
Post Laureate
Reged: 01/02/05
Loc: Lake Tahoe area, Nevada, USA
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Re: 12" Binocular Telescope on Refractors
[Re: KennyJ]
#5661738 - 02/04/13 01:03 PM
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Quote:
I'm surprised at you two not paying more attention to detail ! :-)
Guilty as charged, Kenny! I think term "tricky" can certainly be an appropriate term, particularly in some designs. Having easy to access external adjustments or robust internal ones is essential. If collimation demands wiggling eyepieces or shimming prism turret covers to overcome design or build deficiencies, it's too tricky for me!
Rich
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