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12" Binocular Telescope on Refractors

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#26 Jawaid I. Abbasi

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Posted 27 January 2013 - 04:44 PM

http://www.stathis-f...oerg_28bino.htm
Check this out

#27 GlennLeDrew

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Posted 27 January 2013 - 06:24 PM

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.

#28 GamesForOne

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Posted 27 January 2013 - 09:02 PM

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.

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#29 edwincjones

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Posted 28 January 2013 - 08:07 AM

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

:question:

edj

#30 Mr. Bill

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Posted 28 January 2013 - 02:30 PM

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.

:cool:

#31 faackanders2

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Posted 28 January 2013 - 09:01 PM

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.

#32 CuriousOne

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Posted 29 January 2013 - 07:08 AM

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.

#33 planetmalc

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Posted 29 January 2013 - 11:55 AM

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.

#34 KennyJ

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Posted 29 January 2013 - 12:00 PM

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

#35 ThomasM

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Posted 03 February 2013 - 06:38 PM

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.cloudynig...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

#36 GlennLeDrew

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Posted 04 February 2013 - 07:11 AM

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. :grin:

#37 faackanders2

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Posted 04 February 2013 - 11:01 AM

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.cloudynig...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

#38 Rich V.

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Posted 04 February 2013 - 11:08 AM

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

#39 KennyJ

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Posted 04 February 2013 - 12:27 PM

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

#40 Rich V.

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Posted 04 February 2013 - 01:03 PM

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

#41 ThomasM

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Posted 04 February 2013 - 04:17 PM




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.cloudynig...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


Ken,

I can not give an exact number, it took me almost three years to construct the instrument and I did not count all expenses. All in all, I guess the total costs were about twice as much as that of a high quality comercial 150-160 mm apo refractor.

Thomas

#42 ThomasM

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Posted 04 February 2013 - 04:27 PM

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


just to add one point, the impressive 12" instrument, but also my 160 mm binocular telescope have two knobs (for left/right, up/down each) which allow perfectly overlaying the two images . This mandatory for high magnifiction and very comfortable to use.

Thomas

#43 joe nastasi

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Posted 04 February 2013 - 04:45 PM

Nice project but a near perfect 16"-18" equatorial Newtonian with a high quality binoviewer will outperform it for $490K less.

#44 ThomasM

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Posted 07 February 2013 - 05:25 PM

Nice project but a near perfect 16"-18" equatorial Newtonian with a high quality binoviewer will outperform it for $490K less.

Assuming that this is correct, why does somebody who can affort it waists so much money?

:question:

#45 GamesForOne

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Posted 07 February 2013 - 05:54 PM

Nice project but a near perfect 16"-18" equatorial Newtonian with a high quality binoviewer will outperform it for $490K less.

Assuming that this is correct, why does somebody who can affort it waists so much money?

:question:


That is quite an assumption. Such a question risks opening the can of worms as to which telescope design puts up a better image. Frankly, my 105mm TMB-designed APO lens with AP diagonal shows an absolutely textbook star image. Observing double stars with it is a joy with good seeing, with or without a binoviewer.

I've yet to observe through a newt that shows such a sharp and perfectly collimated image with such ease and consistency, especially with increasing magnification, and I've used and owned Zambuto mirrors.

Not to mention the fact that you have no central obstruction from a secondary or diffraction spikes...

If I had the money I sure would enjoy that view!

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#46 Mr. Bill

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Posted 07 February 2013 - 06:10 PM

Nice project but a near perfect 16"-18" equatorial Newtonian with a high quality binoviewer will outperform it for $490K less.

Assuming that this is correct, why does somebody who can affort it waists so much money?

:question:


Because they can... :grin:

#47 Mark9473

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Posted 08 February 2013 - 11:36 AM

Nice project but a near perfect 16"-18" equatorial Newtonian with a high quality binoviewer will outperform it for $490K less.

Assuming that this is correct, why does somebody who can affort it waists so much money?


Without going into the specifics of both instruments or their cost, you need to realize that for a given size exit pupil, the image with a binoviewer is only going to be half as bright as in a binoscope.

So at least on that parameter, take "outperform" with a grain of salt. However there are obviously very many other parameters that come into play in what somebody would call "performance".

#48 edwincjones

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Posted 09 February 2013 - 08:54 AM

Nice project but a near perfect 16"-18" equatorial Newtonian with a high quality binoviewer will outperform it for $490K less.

Assuming that this is correct, why does somebody who can affort it waists so much money?

:question:


take any binocular (or optics) ever mentioned on CNs,
someone would think that it was a waste of money,
either too expensive or too cheap for their tastes

we are a diverse group
edj

#49 Erix

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Posted 09 February 2013 - 07:06 PM


take any binocular (or optics) ever mentioned on CNs,
someone would think that it was a waste of money,
either too expensive or too cheap for their tastes

we are a diverse group
edj


Isn't that the truth, and thankfully so. What works best for one person doesn't necessarily fit the bill for the next. Thanks for that reminder! ;)






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