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Bino frac ??????


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On the back of a silly comment i made in another post, having been up to Peter Drews centre and see so many binocular refractors it got me thinking i could buy another TS80 F7.5 and parallel mount it to form a bino frac.................so first question, would this be worth doing, would it give me a 160mm frac?

second is mounting it, though light it would need to be in Alt/Az to work, on that basis i ruled it out, then while out in garden making a new fence i found myself thinking 18mm Birch ply, and it would be feasible to make a Dob style cradle that moves in alt and az motion, this could be fitted to an EQ5 tripod 

Im not saying i will go ahead with this half baked idea but im giving it thought

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This would be absolutely brilliant, not in the least in light of all the reasons you could come up with not to do it.

:happy11:

It may not give you a 160mm frac but it would certainly give you one 80mm frac for each eye.

Can't wait to see it.

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a mate of mine made a pair from 2 ed80s the old gold type with the single speed focusers joined with a bar, thay worked really well, i remember looking at the moon with them and it looked allmost 3d and super sharp. deff worth a look, he had a homemade az mount for them. charl.

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1 hour ago, nightfisher said:

parallel mount it to form a bino frac.................so first question, would this be worth doing, would it give me a 160mm frac?

There is an interesting read on the benefits of bino vision ( being more than the sum of the parts when the brain adds them up !) in a link that @DRT gave in that other thread. It is about 2/3 the way down that page, if I have copied the link correctly this should take you directly to the section :-  http://www.brucesayre.net/#The_science_of_binocular_vision

 

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I understand binoculars give results equivalent to about 1.4x their aperture. So an 80mm binocular would show similar to a 112mm telescope because you brain knits the two images together and pulls more out of them

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The effect of using a given aperture for each eye rather than a single aperture is very hard to quantify in terms of equivalence. Two 80s absolutely do not give equivalence with 160, however, for this obvious reason: the area of a a single 80mm aperture is 5026.55 square mm. Doubled into binos, that makes 10,053.1 square mm. The area of a 160mm aperture is 20106.19 square mm which is twice that of two 80mm apertures.

It can be done and often is. I've tried a double 11 inch SCT bino made by Ralf Ottow as a test rig for a really big one he's building... However, althought the back focus of the standard SCT was long enough to allow pairs of diagonals in each scope to put the EPs the right distance apart the light path was too long for the scopes still to be diffraction limited. Her therefore ground new correctors and secondaries... Yes, well!

All good fun,

Olly

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Easily(?) enough to do :icon_biggrin: but not quite as straightforward as setting two 80mm tubes in parallel. The 80mm+ optical centres are too wide to meet your eye separation so you need to use additional optical components to tuck them in a bit, then you usually have to cut the OTA's down to reach focus. As already mentioned, it does not result in a 160mm instrument but feeding the brain with two signals instead of one and one noise certainly enhances the image.  :icon_biggrin:

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I will take Peters word as gospel on this subject and due to lack of tools and knowledge put this idea to rest, any was i would miss the appeal of the single 80mm grab an go if i went ahead

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May be of interest:

http://www.aokswiss.ch/d/tel/bino/aok/bb-130.html

http://www.sciencecenter.net/hutech/borg/bino/index.htm


Also, there used to be an outfit called Binoscope that made things called Binobacks, which were specifically designed to overcome the IPD issue with big refractors - look a bit like the back end of the Borgs in the link above.

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As Steve posted, there are options. Using Matsumoto prisms you can position the eyepieces at the correct IPD. AOK Swiss does supply these prisms.

Beat Kohler (owner of AOK Swiss) has a fabricating plant so he could make a binoplatform for the specific scope you mention.

Doesn't hurt to drop him an email. I have bought from him a few items - his English is excellent and he is very customer oriented. Just make allowances as I think he is on vacation now.

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5 hours ago, nicoscy said:

As Steve posted, there are options. Using Matsumoto prisms you can position the eyepieces at the correct IPD. AOK Swiss does supply these prisms.

Beat Kohler (owner of AOK Swiss) has a fabricating plant so he could make a binoplatform for the specific scope you mention.

Doesn't hurt to drop him an email. I have bought from him a few items - his English is excellent and he is very customer oriented. Just make allowances as I think he is on vacation now.

Thanks for the reply but as stated in my previous post its a nice idea but beyond my tools and skills, and to pay some one to make it is beyond my pocket

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