Quote:
Originally Posted by Starkler
Silly question time.
We all would be aware that the subjects viewed are too far away to yield any kind of true stereoscopic vision, so what advantages does a binocular telescope give over a standard one fitted with a binoviewer?
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( Apologies for all ensuing typos here folks !)
Geoff, I've covered this question a few times on various forums but its a very natural one.
For all interested heres a brief run-down on the advantages. The bi-newt effect is not about looking for parallax geberated 3D.
The brain somehow doesn't get fully fooled by beamsplitting device, when it comes to using th eadavatages of binocular vision. . I have compared extensively a true 8" binocular and a 12" with binoviewer, and I find that many of the brains image processing capabilities ( most particularly looking at fainter objects ) do not cut in as well with a beamsplitter. To get the 40% contrast increase afforded by binocular vison, you need a randomly varying signal to each eye. The brain also seems to do more processing when looking through two seperate cores of the atmosphere, than just splitting the same image to each eye.
The contrast enhancing effect in a true Bi-Newt is something obvious, which I don't see so definitevly in a beamsplitter. There is a moment when you first look into the eyepieces where your brain gathers the information. In the course of half a second or so, you suddenly see the background sky which is normally noisy and speckly, turn velvet black and seem to drop off into infinity, leaving the object in stark contrast. Seeing the Horsehead easily without filters was a good example of this. The moment when you first look into the eyepieces and this enhanced visual contrast cuts in is a kind of moment of intuition that you are getting all that is possible that I never tire of. The views of globular star clusters are other -wordly becasue your brain does not make `boiling porridge ' of the view whilst it searches for pattern amongst the threshold stars that come and go. The binocular view makes it 20% more likely that you will glimpse and confirm a threshold star in each eye and youtr brain will fix it in view for you. My first view of Omega Centauri through a 20" binocular confronted me with an object I had apparently never seen before as my eyes weaved down through 3 dimensional voids amongst red giant stars.
Bi-Newts are not so much about pseudo-stereoscopic affects , although they are very pleasant, and some find them very powerful and attractive.. An effect called `chromatic stereopsis' makes red stars look closer than blue ones.
http://www.binoscope.co.nz/3d.htm
This can give globular and open star clusters a very 3 dimensional look. What I find pleasurable with a well adjusted pair , is the impression that I am looking through a spaceship porthole..the window edge beeing fairly close and the view being much further in the distance. I call this `presence'.
A true binocular also shows you more sky area than an equivelent mococular, about 4 times more sky area in fact. Take into account that we are limited to about F4.5 ( for most peoples taste ) regardless of aperture, and the equivelent monocular ( seeing a similar thing by sheer aperture rather than contrast ) is about 40% larger aperture for low light level subjects. Given that a binoviewer on a Newt needs a 1.2X to 1.4X barlow to reach focus and it is of much longer focal length anyway, as rule of thumb you can achieve 4 X more sky area in a single view with an equivelent binocular Newtonian.
There are also issues with cumulative errors inside binoviewers and spherical aberration in them when passing faster light cones through prisms.
There is no doubt that bi-Newts are a very specialised Item. For the majority of people , a larger aperture monocular will always be the easier and preferred option. There has been a little evolution going on lately with Dave Moorehous's 2 Bi-Newts and now Pauls 12". We are sticking to the same basic design and trying to improve on it without getting off track each time. I think we are getting to the heart of a design that can be easily tackled by anyone with a one truss Dob allready under their belts, or at least a methodical approach.
Hopefully we can have a pair at the SPSP for people to look through and experience some of these.
I'd like to add that I applaud the explosion in the market of availability of quality Binoviewers, they are a compact and neat solution to access binocular viewing and the more access to the simple humanity of using both eyes to explore the Universe the better
Mark
Then again - I daren't look through these as mine are going to be 12's...... 
12'' Binoscope
