Bino-viewer with a Dob

[Stu Ward]

I think i read somewhere that you will not be able to achieve focus.
Is this correct ?

I love the thought of being able to use both eyes, and imagine that the stereo view could be something special.

Such a shame if they are not compatible

Stu

[sopticals (Stephen)]

Hi Stu,
If you have the collapsible dob, dont fully extend by around 1" to 2" and binos will come to focus. ( This is the case with Williams Optics with the 1.6x supplied with corrector.) If your OTA is non extendable then primary and secondary mirrors must be brought closer together by 1" to 2"to achieve focus with supplied corrector, otherwise an extention tube (or two ) have to be screwed in between bino end and corrector. This last option has the downside of further increasing magnification and diminishing the size of field of view. In my own case with my 14" f5 dob I moved focusser and spider/secondary assembly 1.5-1.75" down tube thus reducing distance between mirrors and giving myself the extra lightpath length at focusser necessary for focus to be obtained.

[Stu Ward]

I have a 12" collapsible dob, so i can move the secondary closer by this.
What are the views like with the 14" and Bino ?

Stu

[Osirisra (Ken)]

On bright objects they are brilliant. I like using them on the moon, planets, and bright nebs and globs. it's great to be able to sit down, relax and enjoy with both eyes.

[ausastronomer (John Bambury)]

Hi Stu,

Some companies that make binoviewers also produce an Optical Correction System (OCS) that will allow the binoviewer to reach focus with a newtonian. The Denkmeier OCS has been advanced to "power switch" status. Historically a lot of people just used a barlow to bring the focal plane in to allow the binoviewer to reach focus. Shortening your poles or not fully extending them will also enable the binoviewer to reach focus. Depending on the sizing of the secondary mirror it could introduce vignetting as moving the secondary closer to the primary will inherently cause the secondary to be undersized. That having been said the secondary mirrors on the Chinese/Taiwanese scopes tend to be a tad oversized in any case, so with these particular scopes it should work fine. If it does vignette this will be evident by a dimming of the image brightness towards the edge of the FOV.

Also keep in mind that binoviewers work best on brighter objects only because they work by "splitting" the available light into two, which will cause a dimming of the image, which is very noticeable on the dimmer targets. I have used them a bit and to be honest I much prefer the single eye views to using a binoviewer. However, I have been very spoilt with ready access to an excellent 12.5" binocular telescope and a pair of 25 x 150 Fujinon binoculars. By comparison these blow any binoviewer into the weeds and probably causes me to be a little harsh in real terms, on what a binoviewer can achieve.

Cheers,
John B

Cheers,
John BS

[sopticals (Stephen)]

Originally Posted by Stu Ward

I have a 12" collapsible dob, so i can move the secondary closer by this.
What are the views like with the 14" and Bino ?

Stu

Hi Stu, if you want to try binoviewing I would suggest the WO units as price is very reasonable and performance (as most people have found) dosent differ greatly from units that are much more expensive. Would work great with your scope.

I have to say that all my moon walking is now done using WO binos. With mono I used to find moon too bright unless using moon filter.Now brightness of view is just right (because of light beam being split). Two eyed views give that 3-D effect,( moon looks like a globe with vistas clearly showing the curvature of the Lunar-scape) and are much more immersive. With mono viewing moon now looks (to me) like a flat dish in comparison.Also now enjoy full moon observing as bino contrast is excellent.


The Planets are great as well. Saturn and Jupiter are real gems. Had the joy earlier in the year when Jupiter was in the evening sky to watch (in 3-D) Io approach and transit across the surface of Jupiter as a small bright disc (surface detail was a little beyond my visual grasp), but a spectacle beyond any previous one eyed views I had experienced.

Also great on many DSOs like m42 etc and globs. Though for fainter objects I still go mono mode as you go around 1/2 mag deeper, otherwise one has to use a little of the "averted vision" to get there.

Stephen.

[Stu Ward]

Thanks Steven

I think you have made my mind up and I will be going to purchase one of these from Andews on Monday morning

Stu

[Derek Klepp]

I knew I shouldn't have read this post (just recently got a 16" Skywatcher Goto DOB) Stephen do you have any problems with the extra weight on the goto drives?(Had to tighten the locknut on my Alt shaft). By the way Stu views through the 16" are what I've been after but it is big mine is on castors and wheels out on rails.

[Barrykgerdes]

Bino viewers are really only a gimmick. They may help some people with eye problems, particularly on bright object like the moon and planets but in general the action of splitting the light into two paths and the correctors needed to reach focus introduce reductions in light throughput equivalent to reducing your aperture by about 20%.

They do not produce a stereoscopic view as they are only looking at the image from one set of optics. However as already stated the view to be had from some of those 12.5" bino telescopes is magnificent.

Barry

[Stu Ward]

Splitting the light will have a dimming effect i agree, but the ability to use both eyes to appreciate the photons must be beneficial surely.

Purely from an eyestrain point of view, being able to relax both eyes and take it in must improve the experience ?


Stu

[sopticals (Stephen)]

Originally Posted by Derek Klepp

I knew I shouldn't have read this post (just recently got a 16" Skywatcher Goto DOB) Stephen do you have any problems with the extra weight on the goto drives?(Had to tighten the locknut on my Alt shaft). By the way Stu views through the 16" are what I've been after but it is big mine is on castors and wheels out on rails.

Hi Derek,

My dob is a "push" GOTO and "push" tracker. (So no trouble with the drives). As your scope is the collapsable version and you dont extend that last 1 1/2" -2" then the moment of turning about the Alt axis is less and this will offset to a degree the extra weight of the binoviewer and extra eyepiece so shoulnt put undue strain on the drives.

You have got a nice scope, go for all the gadgets,(including binos) and enjoy "scope heaven".

Stephen.

[sopticals (Stephen)]

Originally Posted by Stu Ward

Splitting the light will have a dimming effect i agree, but the ability to use both eyes to appreciate the photons must be beneficial surely.

Purely from an eyestrain point of view, being able to relax both eyes and take it in must improve the experience ?


Stu

Hi Stu,

Yes there is a slight dimming effect,but not as great as you would think.At first glance at the theory it would seem the brightness factor would yield 50% to each eye so that a 12" aperture scope with binoviewer would be equivalent to an 8.5" scope in "monomode" as regards its ability to reveal faint objects, BUT, there is the factor of "light summation" to consider, whereby when both eyes send the received (simultaneous) signal to the brain a 1.4x increase in brightness is the result. Now this has the effect of taking your image to the level of a scope of 10" aperture. So overall though there is some loss in intensity of light in the binoviewed scope as comopared to same monoviewed scope its not too great.

Summation (like two cylinders firing instead of one) also (for most observers) has the effect of increasing both contrast and resolution by an apparent factor of up to 1.4x also. So your 12" scope (in binomode), can seemingly can give the contrast and resolution of a 16"-17" with one eyed views.

And yes eyestrain is much less.(One eyed squints can never please the optical receptors in the cerebal cortex like natural two eyed views).

Stephen.

[ausastronomer (John Bambury)]

Originally Posted by Stu Ward

Purely from an eyestrain point of view, being able to relax both eyes and take it in must improve the experience ?


Stu

Stu,

I know some very serious lunar/planetary observers and NONE OF THEM use binoviewers. They can give a nice view, but you simply cannot see the same level of detail as you can in cyclops mode and as I said before I prefer cyclops mode. As Barry said they are somewhat of a gimmick. I know a lot of people who bought them because they could. Used them because they could and when their observing skills progressed to a higher level the binoviewers sit unloved in the accessory case. That having been said there are some experienced observers who use and enjoy them. They are not the magic bullet some would have you believe they are.

Cheers,
John B

Cheers

[Poita (Peter)]

I think calling them a 'gimmick' is a bit harsh. Binoviewers are no more a gimmick than binoculars are, or remote viewing or manual tracking or any other way of viewing that may have some drawbacks compared to other methods.

The 3D effect is basically the same with astro stuff using binoculars or binoviewers. In theory the binoculars should be 3D and the Binoviewers 2D because the binoviewers share a single optic and the binoculars one per eye. However at astronomical distances the stereo separation is effectively zero, so the '3D effect' is created by the brain and not via stereoscopy in either case. The human brain relies on far more than just ocular separation to process an image into 3D, and with subjects like the moon there are plenty of depth cues for the brain to build up a 3D map.

Just because certain experienced viewers do not use them doesn't make them a gimmick either, they have their pros and cons like any piece of equipment.

They let you use both eyes at once which is a distinct processing advantage in the visual system of the brain. They allow you to view with more comfort and for longer. They allow the brain's 3D processing systems to kick in, separating data by depth based on visual cues. You lose some light due to the splitting of the optical path, but you gain quite a lot back by having two eyes gathering light.

It is a different viewing experience, one that has worthwhile advantages for many. If we only ever viewed the absolute highest resolution methods, we wouldn't even venture outside without traveling to the highest peaks on only the clearest of nights. Like anything, there are compromises, but they are far more than just a gimmick.

The view through my binos out here under inky skies would yield more resolution than anyone in the city will get in cyclops mode.

[Satchmo]

I find the view in binoviewers very flat and lifeless. The brain is used to seeing a slightly different image in each eye and in a binocular scope this is because the seeing conditions are slightly different at any one moment. This effect makes the view look more `real'. Also for planetary viewing the seeing may be better at any one instant than the other.

Once the brain picks up a detail if it can be reinforced by the other eye - even fleetingly it tends to lock the detail in much more solidly. In other words the seeing will look better with two eyes than one. With a binoviewer this extra image processing doesn't take place.

I find for deepsky observing you can never replace the lust re of wide exit pupil because each pupil only has half the light content. A true 5mm pupil in a binoscope is a wonder to see. The 40% contrast gain means that the background sky looks darker and more contrasty.

All that being said in practical terms binoviewers are easy to obtain and relatively cheap, and probably outnumber binoscopes by 10,000 : 1 in popularity. So there is a lot to be said for them. And with the right accessories you can use them on all your scope..

[Stu Ward]

Now i'm really confused !!!

[Poita (Peter)]

I find the mono viewing flat and lifeless compared to the view through a binoviewer, but the view through a binoscope is certainly another step up.

At any rate, the Williams Optics Binoviewer is about $210 shipped, and comes with two eyepieces and a Barlow, and they quickly sell second hand for around $180, so anyone who wants to see what binoviewing is about, can do so for very little money, and if they don't enjoy it, can turn around and sell it and hardly be out of pocket.

For me, a binoviewer adds a lot of enjoyment, makes the scope more accessible to more people and gets the kids and partner involved, and gets me out on nights I normally wouldn't bother, and keeps me out there viewing for longer. Anyone else's mileage will vary of course.

[Stu Ward]

Where did you get it for $210 ?

[Stu Ward]

I just bit the bullet and ordered through WO Online
$215 inc shipping

Wonder how long for delivery ?

Stu

[Poita (Peter)]

Mine arrived in about a week.