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gatorengineer
scholastic sledgehammer
Reged: 02/28/05
Posts: 882
Loc: Hellertown, PA
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I am thinking about using Meade Schmidt Newt 6" scopes for making a large binocular. I want to minimize alterations to the OTA's so I am thinking about orienting the two focusers towards each other at a 45 degree angle (from vertical). Then using either 45 degree erecting prisms, or Schmidt prisms to bring the light back to vertical into the eyepieces....
I want to use 2" eyepieces with the bino, and I have found by "playing with" a traditional 90 degree mirrored diagonal I lack the infocus necessary, I think 45 Prisms are short enough light path....
Would this work or would I end up with two reversed images. I think it works but I want to be sure before I undertake....
Any other comments would be appreciated.
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20" F5 Dob
16" Dob in pieces
Comet Catcher
MN71
12" Doc Clay Sky Patrol MEADE SCT
12.5" F4 Newt under construction
Siebert 45mm Binoviewers
Lots of binos---
Optics Past - 8" Stf Mak, 4" B&W triplet, 6"Schmidt newt, 12"LX200, C8, Meade LX10-10", 10" MEADE ACF, SN8, TAL150K, Orion 150MC, Jason 60mm refractor, ATM 6" F8, WO 110FLT, 92mm Off Axis Newt, Televue Genesis, Nikon 20x120 bino's, 15x110 Boarderguards, Kuhne Flaks
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jg3
sage
Reged: 05/27/07
Posts: 329
Loc: near Auburn, CA
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I think your images would not be oriented the same. Please, please teach yourself a way to figure out reflections, with diagrams, a card-paper and TP-tube mockup, whatever.
The usual way to make a newtonian into binocular is with a third (tertiary) mirror above each focuser, sending the light skywards, parallel to the OTA's axis. When viewing, the back of your head is in the direction of what you see. The image is reversed due to three reflections.
The OTAs can be in any relative orientation in axial rotation. Consequently, one of the ways to adjust interpupillary distance (IPD) is to rotate the tubes.
One thing about those SNs is the high focal plane, enabling SLR cameras and other deep-focal devices to be used, after taking out the drawtube extension. This gives you some distance for a bino-scope's tertiary mirrors, which you'd put on *without* the drawtube extension. (I still don't know for certain there's enough distance. You might want to try with one SN and a borrowed diagonal.)
Yes, at f/5, 2-inch eyepieces would be good to be able to use. But 2-inch star diagonals would collide with each other at such wide IPDs as to be useless. But if you were to go up a step to the 8-inch f/4, you could skip the trouble and use 1.25-inch eyepieces and diagonals, and probably end up with a finished bino and a good range of eyepiece pairs for less total cost! (A little less total field of view, though.)
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gatorengineer
scholastic sledgehammer
Reged: 02/28/05
Posts: 882
Loc: Hellertown, PA
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Thanks for the input, the plan was to use the prism as the tertiary, sorry if that wasnt clear, its my failure to write clearly, brain thinks faster than typing..... With a Tertiary mirror, (refractor diagonal), not enough focal length, above the tube....
I want to use a pair of Ethos 17s, and the SN I plan to use is the F3.6 variety of the 6". This yields roughly a 32 x 153, with a 3.1 degree field of view.....
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20" F5 Dob
16" Dob in pieces
Comet Catcher
MN71
12" Doc Clay Sky Patrol MEADE SCT
12.5" F4 Newt under construction
Siebert 45mm Binoviewers
Lots of binos---
Optics Past - 8" Stf Mak, 4" B&W triplet, 6"Schmidt newt, 12"LX200, C8, Meade LX10-10", 10" MEADE ACF, SN8, TAL150K, Orion 150MC, Jason 60mm refractor, ATM 6" F8, WO 110FLT, 92mm Off Axis Newt, Televue Genesis, Nikon 20x120 bino's, 15x110 Boarderguards, Kuhne Flaks
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deSitter
Carpal Tunnel
Reged: 12/09/04
Posts: 2926
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Impossible I'd say - so go for it 
-drl
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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1296
Loc: Ottawa, Ontario, Canada
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Some years ago one of our club members (now deceased, unfortunately) made a bino from a pair of Celestron Comet Catchers (5.5" f/3.64.) They were designed so that the eyepieces pointed toward the target, i.e., the back of the observer's head faced the target, and he looks downward in the direction of the primaries.
I can't recall with certainty, but he may have used two mirrors. My preference would be to try it this way...
Use an Amici prism, but oriented so that it sends the light toward the back. In this way you'll be facing the target, just as with a normal straight-through bino. Of course, you have to make sure that your head can fit between the tubes.
An Amici prism offers two advantages:
- Its roof makes two reflections, and with the two reflections in the 'scope you have a non-mirror reversed view!
- The thick hunk of glass moves the focal surface further back by a distance equal to 1/3 the glass thickness. This gives you a bit more room to work with.
This idea was inspired by the 'Bazooka' 'scope plan in one of the good ol' Sam Brown/Edmund books.
As for a source for an Amici prism, I'd recommend the 2" format 90 degree type, which has a quite generous 40mm clear aperture (the smaller 1.25" speciments have only 21mm aperture, although you can still use eyepieces having up to 25mm field stops without bad vignetting). William Optics carried them (and may still), although I got a pair for much less $$ from Orion, who I suspect no longer have 'em.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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timo4352
super member
Reged: 04/16/07
Posts: 160
Loc: Northeast Ohio
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These pages might help:
http://astrosurf.com/eroyer/BinewtDesigner/Binewt.htm
Tim
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Orion 3.6CA Reflector
and 2 homebrew scopes --
8" Hubble Bubble ballscope
8" F/8 CHief - nearing completion
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