Binoviewers - why did i not do this before!

[LukeSkywatcher]

Binoviewers seem to be amazing things. The only problem i can see (no pun intended) is that you need 2 of every EP to either go up or down in magnification. I'm thinking that could become VERY expensive?

[Andrew*]

The problems with binoviewers are manifold. For example, you lose about a magnitude of brightness due to the light being split in two.

Focus issues are very common.

Some people just don't get on well with them, not managing to merge the views completely, and it can be straining for them to view with them.

On the right targets, and when they're set-up right, they are very nice, and in my experience, very relaxing, to view through.

Andrew

[dweller25]

Russ, pleased your enjoying the binoviewers.

I find using two eyes gives a little more contrast than in cyclops mode and floaters disappear. I can also look at the view much longer allowing me to catch that brief moment of excellent seeing.

[Towa]

Binoviewers seem to be amazing things. The only problem i can see (no pun intended) is that you need 2 of every EP to either go up or down in magnification. I'm thinking that could become VERY expensive?

With my refractor I can go from 40x, all the way up to 400x with just one pair of Antares 20mm Plossl eyepieces. By using different combinations of where you put the Barlow lens and an extention tube you can have a huge range of magnification.

[great_bear]

With my refractor I can go from 40x, all the way up to 400x

Does image quality suffer by "straining" a Barlow in this way?

Any CA issues?

[ZOG]

Thanks for the report Russ. I've been toying with the idea of bino viewers, my problem being that my right eye has an astigmatism and is "lazy" which is why I haven't had laser surgery on it as they say they can fix the astigmatism but the eye would remain lazy so there would be no real improvement. I do all my observing with my left eye, I even shot with a rifle left handed when I was in the forces.

Can you focus each EP independantly on the revelations or do they just focus as a pair ?

Bill

[great_bear]

Can you focus each EP independantly on the revelations

They can be focussed independently.

[great_bear]

OK! Well, my binoviewers arrived last week, along with the (immaculate) extra Plossls I got off Graham here.

First thoughts:

• Grease is the word, is the word, is the word... - I keep resting my finger in a greasy patch in the hinge. Annoying.
  
• I assumed they might have been unsuitable for daytime use, since the prisms polarise the light for each eye in different ways. However it turns out that since they only partly polarise the light, a correctly orientated polarising filter in the nosepiece cures this problem at the expense of a little light loss. Not that I am anticipating any terrestrial use - it was purely for technical interest.
  
• The above also means that a variable polarising filter can be successfully used with these binoviewers provided that the fixed element is carefully orientated first.
  
• These Revelation binoviewers have a restricted aperture of ~20mm - however this is equally true of more expensive units, such as the William Optics binoviewer. It didn't seem to adversely affect anything.
  
• The prism coatings appear very effective on inspection.
  
• There's a mysterious little circular cap on the silver body of the top face. Could whatever's under there be for the fine colimation of the prism of one eyepiece?
  
• With regard to some people's inability to merge the images, I wonder if their units arrived simply knocked out of colimation? (this is sometimes the case with binoculars)
  
• The shoulder of each eyepiece holder should have been made taller, as it doesn't fully accommodate the Revelation Plossl barrel length. It's not a big issue really.
  

Then we come to the views:

WOW!

I knew they would be good - but wasn't expecting this good!

My MAK 180 Pro effortlessly handled the extra focus, and (like all primary mirror-moving focus systems involving a non-flat secondary) the focus deviation affects the overall focal length of the scope.

So, even without using my barlowing nosepiece from the Revelation Photo-Visual kit, there's some extra magnification involved. I'd say it makes 20mm Plossls effectively behave as 15mm ones by changing the 2,700mm focal length of the Mak into ~3,600mm (the concept of a 3.6 metre focal length in such a compact scope does my head in a bit...)

Anyway, since the Mak 180 Pro is an F15 scope, 15mm eyepieces are ideal. Similarly, now acting as F20 (with the extra focal length provided by refocussing), 20mm eyepieces are ideal - in both cases providing magnification equal to the scope's aperture in mm, whilst providing a decent 1mm exit pupil for good brightness before entering floater-infested-soup territory.

Now, whilst it is true that (by necessity) a binoviewer will halve the amount of light going to each eye - and even more when taking prism inefficiencies into account - in most cases this doesn't matter. The extra boost your brain gets from getting two images more than makes up for it.

The view through my 20mm Plossls was astounding to me.

It was far easier to snap things into focus, and life's everyday minor optical annoyances revealed their true source immediately so you can fix them. In other words, with all of the following everyday hazards:

• Junk in my eyes
  
• Muck on the lens
  
• Poor focus adjustment in one eyepiece
  
• Misting of eyepiece
  
• Clouding of skies
  
• Mist in sky
  
• Floaters inside my eyes
  
• 'Seeing' effects (rippling etc.)
  

- they could be much more quickly diagnosed than before. Without a binoviewer, a "mucky view" could be any of the above, and you need a bit of detective work to discover which. When using the Revelation binoviewer your eyes do the detective work for you, and immediately you know what's up and what corrective action you can take. It's hard to explain, but ou just "know" what the problem is, once you use both eyes.

Star Testing through a binoviewer is heavenly. It is literally like being in the presence of an Angel. Well, maybe that's a bit strong, since I don't think I've been in the presence of an Angel before. Erm... Except my wife, or course... Naturally!

What I mean is, your defocussed star image's diffraction rings just dance in the "seeing" beautifully before your eyes, in a way I found deeply moving and hypnotic.

Arcturus was mesmorising in such a test.

Saturn was fantastic. I only said goodbye to it because it disappeared behind the trees. Even when pushing the magnification up higher using various combinations of barlowing and/or other eyepieces, it held together well.

I tried M13, but (as you know) I can't really see any fuzzies from my location (not helped by lack of eye-adaptation either). From what I could faintly detect, I'm expecting a real treat next time I'm in Devon.

Finally, when going back to single-eye viewing experimentally, there was a sense of being badly handicapped.

In summary: I'm hooked - this changes everything...

[Leswold]

Hello all,

Just joined the site. Just got a Meade LX200 10". Can those of you that know about binoviewers recommend a suitable one for the scope that I have, I understand that you pay for what you get, would rather go for quality than cheapness. Many thanks . Les