Telescope Reviews: Hexy 635mm binoscope update and pics

Monsignor,

That's bizarre, and I'd recommend you disregard such. Tryin 2 wrap my head around what he did is givin me the only headache I've ever had. You have all you need with yer adjustable focuser plates (we had to shim ours). Normal reflector FAET aside, we, like any refracting star diagonal user, simply need to retain a good 90* angle off the primary and secondary for image integrity. But since you asked, and before we go there, when's the last time you heard of "coning angles" in anything other than helicopter/wind turbine rotor blades? Do you remember anything about coning angles from yer binocular days? Nope. Only that collimation required parallelism in the two light paths...(Dunno why people seem to get all weirded out about bino-scopes when they're perfectly comfortable with binoculars [whose oculars ARE NOT tilted 4* BTW])

You'd be referrin to this amazing, ultra-fine bino-build (scroll down page for pic)...

http://stargazerslounge.com/topic/66123-diy-16-binoscope/

And to this from the maker:

"One thing I've not seen on other binoscopes is the coning angle I've put on the eyepeice holders. The eyepieces have an included angle of 4 degrees.

When I did the last 12" bino I used to get eyestrain fairly quickly and eventually guessed it could be from looking down 2 parallel eyepieces but trying to form an image, say, a metre in front of me. I think it was confusing my brain!
So I angled the eyepieces in on that scope and it cured the problem. It was really comfortable and natural to look through after the mod. So I did it on this one from the off.

The worst bit was getting everything aligned. As the main mirrors track up and down the centre tube then the mirror sets had to be not only aligned with each other, but parallel in both planes to the centreline of the main tube.
We had water tube levels, plumb bobs and all sorts of lasers filling the workshop on that day!

I've set the left hand side as the datum and any little tweaks to get a nice comfortable image are done on the right hand secondary mirror. This only needs doing sometimes after changing eyepieces."

And lower down on page 2 someone asks, "I would have thought one of the problems is co-aligning the two mirrors so that the field of view is reasonably common between the eyes? I guess the brain is more tolerant of a mis-alignment than a camera, but how good does it need to be?? I guess you have collimation screws on the primaries?"

Notice that the OP bino-builder was GUESSING his eye-strain and headaches (from his earlier 12" build) were "from looking down 2 parallel eyepieces but trying to form an image," which is exactly what collimated binoculars do. Strange. Stranger still are the steps that he took to "correct" this in his second build. Don't even wanna go there, ok? Instead...

When we first began lookin into the bino-scope we commonly got people--includin our optician--confusin certain bino-viewer "fixes" or adjustments with what we were doin. BUT WHAT WE'RE DOIN IS ACTUALLY MUCH MORE STRAIGHTFORWARD. We're just makin a scope for each eye and taping these together. Period. Now if the bino-builder yer referencin wants to tilt his EPs for comfort/to avoid kidney-beaning, etc., fine! Sometimes we do that and sometimes we don't, because sometimes the EPs get tilted anyway. It doesn't matter. And it certainly doesn't matter for merger. There was sumthin else off in his optical path alignments, and for these simply look to "binocular collimation." The only thing that applies to us eye-strain/headache -wise that doesn't usually apply to normal binocular collimation is the magnification difference of the primaries (not exceeding 2% for military specs, and others say this can be even greater w/o detriment). That's it. The reason that the OP has "not seen on other binoscopes ... the coning angle [he's] put on the eyepeice holders," is because it simply doesn't apply.

Funny, but the other poster there that I pasted above had it right, and they didn't even have a bino-scope (but maybe they had binoculars?). Even a regular reflector build has to be made "square," so we're no different. Collimate each tube separately and we're basically home. You'll see the same star field in each eye. Where there's separation, simply tilt the primaries--or tubes in yer case--til they join. That's it. Ouch. Think I'm gettin a headache.