Bino viewing opinions

[Barry-W-Fenner]

Hi all,

Inspired by the recent thread below.

We touched on bino viewing. I thought it would be a good idea to start a separate thread on the cons and pro's of this set up.

I know a few members use them, However other than the obvious stereo view I dont know what benefits they offer. I have read about better contrast and a "3d view effect" that they apparently give, But do they give sharper more immersive views than the standard mono view.

Why do Binos usually use a pair of lower power eye pieces? I have seen that 17-20mm seem to be the norm.

The appeal of using both eyes is of interest to me, along with the above benefits.  Is the outlay of a pair of binos and 2 decent eye pieces worth it?

I would be using these on my 300p dob in the bino view setting.

Thanks in advance.

 

Baz

[Peter Drew]

For me, binoviewing for solar, lunar and planetary provides a big upgrade in visual performance and enjoyment.  Bright DSO's also look more submersive albeit dimmer than monovision.  Not everyone gets on with binoviewers though, best to try before you buy if possible.     🙂

[ShrewView]

For me, binoviewers do greatly improve my viewing experience when it comes to the moon and planets and on the moon it is more immersive. I find it much more relaxing to have both eyes open than it is using one, and either covering the other to keep out stray light or closing it. I think this is key to why they appear to show more detail. Anything you can do to make your viewing more comfortable allows you to concentrate on what you're looking at. They don't suit everyone though, and you do have to tweak them a bit to get both eyes right, but this isn't difficult.

I think the reason for the low power eyepieces is that the corrector fitted to the binoviewers acts to magnify the image, so with the william optics ones I use, the supplied 20mm eyepieces act more like 10mm.

The image you get is less bright than a single ocular though, so for me they are a much poorer thing to use on deep sky stuff. They also add weight to the setup and alter the balance point and I've heard that some scopes don't always have enough focus travel for them to reach focus, although all mine do.

Best to try before you buy if you can.

[vineyard]

Great Q. I'll defer to other more experienced SGLers, esp as I've never used a Dob so I don't know what BVs on a Dob are like from a practical perspective.

I like them on my fracs.  Definitely more immersive, and overall restful.  I've noticed less floaters at high power if I use both eyes vs just one eye - don't know why that would be?  The moon is pretty amazing in BVs, and you do feel as if you're floating in space.

From what I can tell, the general lower power EP is perhaps for two reasons (a) quite often you need to put a GPC in there that has a magnifying effect, and/or (b) the BV's do dim the view as the light is split so perhaps they larger exit pupil of longer EPs offsets that?  (But I could well be misunderstanding).

One Q I've often puzzled over though is the clear aperture of diagonals for BV'ing.  V often they get marketed as having, eg, 30+mm clear aperture.  For slower scopes I guess that makes sense.  But for a fast scope, I think the image size by the time its gets to the end of the OTA (where the focuser is) will v often be <1.25" anyway, so what difference would it make to have larger clear aperture?  For example, on my little 72ED which is f6 432mm f/l and 330mm OTA length.  By my calculations, the image size will be 17mm by the time it gets to the end of the OTA (ie, even before factoring in any racking out) so there's not much point in having a larger diagonal - I won't see more FOV.  Or am I getting that wrong?

I have no idea whether would still be the case w Dobs though.

Cheers

[sputniksteve]

I'd love to have a guy with some. But my eyes are incredibly different, with the vision in my right eye being pretty poor, whilst my left is short sighted but otherwise ok. I'm not sure I'd benefit from bino viewing.

[Mark at Beaufort]

Barry the views through binoviewers can be really special especially observing the Sun, Moon and the Planets. However, the reason many use low power EPs is because to gain focus you may be required to use a barlow.

When I had a 4" Apo frac I had to use a 1.6x barlow and even then the focus tube was right up to the buffer. The 180mm Mak/Cass did not need a barlow and the views of the planets (especially Saturn) was fantastic.

Now the problem with Newtonians - both my 6" and 12" Dob could gain focus but I had to use 2 barlows making the magnification very high although the views were pretty good. You maybe fortunate having the 12" flextube because you can move the focuser nearer to the primary to gain focus without the need for a barlow. Maybe someone on the forum has tried this arrangement and can report their findings.

[MartinHiggins]

Hi, I got a pair of Williams Optics binos about 3 years ago for use with a Celestron C8 and in fact I can't recall the last time I observed with a single eyepiece.

[bomberbaz]

I love viewing the moon through my binoviewers although I use a mak, very immersive and yes it does give a 3d perspective although I think it is more your brain telling you this rather than it actually being the case. I am looking forward to having a bash at Mars with them as soon as the clouds clear. 

Thing with BV's and barlow is there is an amplification of the actual stated magnification due to the increase distance in focal train. Just BV's on there own add x1.15 to the magnification on my mak, don't know if the dob will work the same as the optical arrangement is very different.

Now with a 1.6 barlow added to the BV nose this is actually taken up to x3.2, change this to a 2x barlow and it goes to x4. This is as mentioned due to the increased focal train distance and I would expect similar in your dob although again I cannot confirm exactly what the case will be as I have never used in one.

FYI I use a pair of 25mm Vixen NPL eyepieces in my BV.

Oh something worth mentioning is if you use a tele extender such as a powermate then there is no amplification of because of the focal train. So a 2x increase remains 2x. 

Hope this all makes sense but there is an article below that kind of explains this and was based upon testing and technical knowledge of a few members including myself.

 

[Rusted]

Seeing the moon through binoviewers is more like hovering above the surface than merely peering at it with one eye.
I find it relaxing and detailed with no obvious floaters. Same with the sun in W/L and H-alpha.

The increased magnification has already been mentioned as [probably] the major downside.
The Glass Path Correctors are placed a long way from focus with binoviewers.

I use pairs of Meade 4000 32, 26 and 20mm Plossls.  26mm more than the other two.
With my TS binoviewer I have TS 1.6x, 2x and 2.6x GPCs. 
I believe these are their true powers when used on the snout of a binoviewer.
They are weaker when used on the nose of a single eyepiece or camera.

More expensive binoviewers should give you much greater clear aperture.
For using lower power, wide angle eyepieces, without vignetting.
Best to check this before buying.

[Ships and Stars]

As others have said here, viewing the moon through binoviewers is in itself breathtaking. My best lunar views hands down have been through my 300p flextube with some second-hand Williams Optics BVs and their 20mm eyepieces.

I also have some cheap 25mm, 32mm and 40mm Revelation plossl pairs for my binoviewers but I often prefer the 20mm WO EPs unless I'm looking at really faint stuff then I'll drop to 32mm or 40mm.  At high mag planetary etc binoviewers reduce the impact of floaters in your eyeballs, something I really notice with one eye at high mag (probably 222x on up, definitely over 300x). Eye strain for me is also greatly reduced using binoviewers as well for extended viewing and I can really settle in and observe with them for longer periods than a single EP. 

As you mentioned, the 300p flextube has a handy binoviewer setting which allows the use of BVs without a 1.6x or 2x glass path corrector by lowering the secondary down to the first click stop on the truss rods. Apparently the downside to this is the secondary becomes a larger obstruction as it sits closer to the primary mirror reducing image brightness, but you get a considerably wider field of view. I haven't used this setting much - need to try it more, especially on faint DSOs but I keep forgetting!

The main drawback for DSO junkies like myself is that the light is halved to each eye making already faint DSOs fainter, but binocular summation makes up for a fair bit of this in my opinion.

One thing to be aware of, the exit pupil for EPs in binoviewers is also greatly reduced. It works out a lot different than using a single EP.

I was able to see the Horsehead with direct vision using binoviewers in a 20" dob under dark skies but it was still a challenge. I wrote a long-winded report on this below - a tip from @jetstream helped a lot as I ended up using a pair of cheap 40mm plossls to see the Horsehead that night. Normally a 40mm plossl gives a ridiculous 10.6mm exit pupil in my f4 dob with no GPC. However, in binoviewers on the same f4 scope with a 1.6x GPC, the 40mm plossls had an approximate exit pupil of 4.49mm. Otherwise I'd never bother with 40mm EPs in any of my dobs.

My suggestion is perhaps find some decent second-hand ones if you can and see if you like them, if not, you can sell them on quite easily, or just pick up a set from OVL etc. It takes a little bit to set them up and get individual focus, but once you've done it a few times it's easy enough to do.

 

 

 

 

[John]

I think the above advice to try and find a low cost pair to try out is excellent

I've tried binoviewers out a few times over the years in refractors and my dobsonian and have found that they are not for me.

Others do find them very good I know so you need to find out if they are good for you 

 

 

[Paz]

I'm going through the binoviewer learning curve and it is taking me a while and a lot of practice and trial and error to get a set up that works for me.

The one clear cut benefit I have found so far is that it takes less effort to observe with both eyes so I am finding myself spending more time on targets and being more relaxed. It's a bit like the benefit of observing seated rather than standing.

[niallk]

I found Baader Maxbrights very good on planets in my 10" dob.  I used a lovely pair of 15mm tv plossls and a 2.6x GPC.  Really great step up from mono, imho.  Excellent on the moon too.  I personally recommend experimenting.

I observe planets mono with my 15".... but not by choice - focus issues with my binov gear   Anyhoo its main job is DSOs, but its mono planets have delivered best ever views on Jupiter, Saturn, Mars.

I once observed the sun in Ha during a nicely active phase in a LS60DS with a TV binovue.... unbelievably exquisite!  I observe mono in my LS50DS, but those bino views are burned into my memory

 

Edited October 20, 2020 by niallk

[Louis D]

There are several advantages to using longer focal length eyepieces with a Barlow/GPC/OCA/OCS:

1. The light cone is slowed down allowing lower cost eyepieces to perform well.

2. The eye relief is better in longer focal length eyepieces which makes viewing more comfortable.

3. Longer focal length eyepieces are less likely to magnify collimation imperfections in the binoviewer.

[Rusted]

4 hours ago, Louis D said:

There are several advantages to using longer focal length eyepieces with a Barlow/GPC/OCA/OCS:

1. The light cone is slowed down allowing lower cost eyepieces to perform well.

2. The eye relief is better in longer focal length eyepieces which makes viewing more comfortable.

3. Longer focal length eyepieces are less likely to magnify collimation imperfections in the binoviewer.

All good points but I find excessive eye relief a nuisance.

Preferring the gentle, head locating effect, of the twin eye cups, for relaxed, extended comfort.
I bought pair of 40mm Plossls for achieving lower powers with GPCs and have never used them again after the first trial.
Oddly enough I found my head could not remain steady at the precise position required without any physical clues.
26mm followed by 32mm are my usual "weapons of choice." 

[Stu]

It took me years, and I think three or four pairs of binoviewers to get used to them to a stage where I get the best out of them (I’m now on my sixth and seventh pair I think!) For some it is easy, but for others I think a lot of brain retraining is needed. My eyes are quite different and it took me quite a while.

I primarily use them for solar and lunar observing in my 4” scopes. At high powers/small exit pupils I suffer from floaters and whilst binoviewing doesn’t get rid of them entirely it makes them much more manageable. 

I do use them for planetary viewing at times, but sometimes still prefer mono despite the floaters. I’m increasing moving towards my 6” and 8” scopes for planetary for that reason.

I use longer focal length eyepieces and barlow them, at times to crazy degrees to get to high powers. In my PST mod I use 32mm and 40mm eyepieces with a x2 barlow. As Rusted mentioned, eye positioning due to long eye relief can be a problem here, as well as glare and reflections caused by your eye being further from the exit lens. I use home made foam eye guards to give me a physical cue to where to keep my eye, and to cut out the glare.

For the Moon and Planets I use 25mm ex microscope eyepieces, with a x1.7 GPC, x2 barlow and often extension tubes as well to get up to x200 ish (although I’m never quite sure of the Mag!) I find this preferable to using shorter focal length eyepieces, and I just add or remove extension tubes to change the mag.

A couple of critical things make a big difference. First is setting the inter pupillary distance correctly so you make sure you get a fully illuminated field in each eye. The second is to ensure you balance the focus correctly to get a sharp image in each eye. This really helps with image merging and ensuring you see the maximum detail.

To date I prefer mono viewing for double stars and deep sky objects, somehow I just prefer the feel of the view.

Hopefully you will take to them like a duck to water, if not, do keep experimenting as they do have real benefits.

Sorry for the long post!

[astro_al]

I only ever use binoviewers these days. I have a problem with my dominant eye taking longer to focus than the other so viewing mono causes me all sorts of problems when I look away from the EP. I doubt I would go back even if I could though. I had years of short eye relief orthos and mimimal glass setups, which was great but no where near as relaxing as binoviewing.

Regarding EP selection and glass path correctors, I always found the quotes by Roland Christen posted here very useful: http://www.darksights.com/Binoviewers.htm

[garryblueboy]

It took me several attempts to find the right pair for me and I’ve found them it’s so much easier to view with both eyes more relaxed 

and the views are stunning I still view mono occasionally but prefer the the combination view through the binos 

[bomberbaz]

On 19/10/2020 at 10:49, Peter Drew said:

For me, binoviewing for solar, lunar and planetary provides a big upgrade in visual performance and enjoyment.  Bright DSO's also look more submersive albeit dimmer than monovision.

Seen this mentioned several times, maybe some one can shed more light onto this.

My thought being we all know the brain to sight link a smart thing and play strange tricks on you making things look different than they really are.  So I had the idea that your brain might stack the images it is receiving to actually make them look brighter.  Two being better than one as they often say. 

Edited October 24, 2020 by bomberbaz

[Peter Drew]

Just look at anything during the day Steve, then close and open one eye, the view doesn't noticeably get brighter or dimmer.  The brain doesn't stack two images but likes the two sets of signal provided by two eyes rather than one signal and one noise to sort out.     🙂

[bomberbaz]

3 minutes ago, Peter Drew said:

Just look at anything during the day Steve, then close and open one eye, the view doesn't noticeably get brighter or dimmer.  The brain doesn't stack two images but likes the two sets of signal provided by two eyes rather than one signal and one noise to sort out.     🙂

Thanks Peter, good point well made. However  then how is an object noticeably dimmer given you have only the BV prism and some extra glass of one more eyepiece? still don't get that. 

[Peter Drew]

The problem is, the prism used in a binoviewer is a beam splitter, this sends half of the light to one eye and the other half to the other eye.   Therefore the eyes get only half of the input light and the brain, unfortunately, doesn't  recombine the light.  With binoculars or binoscopes you get the full amount of light in each eye, the perception, in this case is that the combined light appears to be brighter than a single telescope of the same size.    🙂

[bomberbaz]

3 minutes ago, Peter Drew said:

The problem is, the prism used in a binoviewer is a beam splitter, this sends half of the light to one eye and the other half to the other eye.   Therefore the eyes get only half of the input light and the brain, unfortunately, doesn't  recombine the light.  With binoculars or binoscopes you get the full amount of light in each eye, the perception, in this case is that the combined light appears to be brighter than a single telescope of the same size.    🙂

I always thought our brain was smarter than that too 🙄. 

Seriously i watch a lot of science and nature type TV and am always amazed at the things animals, including ourselves achieve or perceive because of the power of brain power. 

Anyway, I had no plans for deep sky viewing with BV's but just wondered.

Thanks for the input Peter.