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collimation issue?

Started by rnc39560, 03/27/2015 03:03PM
Posted 03/27/2015 03:03PM Opening Post
Ok... I don't post here often, obviously few do looking at stats, normally do my buying and poke around classified. The "other" site isn't too speedy on my phone right now, and I'm HOPING I can get a question answered.
I just now received a new pair of 20x80 from Orion in the current sale. However, when I first look through them, its a "slight" eyestrain, then gets better. When I look away, Im cross eyed for a second and then it stops. I've never looked through 20x80, but this doesn't seem normal. The image is clear and not double, but induces eyestrain and when I look away I'm briefly cross eyed for a split second.

Celestron c102, 9x50 RACI finder, GLP
XT8, 9x50 finder
10x50 and 16x32 binos[COLOR="Blue"][/COLOR]
Posted 03/27/2015 03:49PM #1
I worked Physiological Optics at the Boynton Center for Visual Science at the the U of Rochester, so am kind of into this stuff. I no longer remember the vergence specs for bono instruments, but it is pretty relaxed...which is to say that our eyes are fairly accommodating to merge LR images. Telescopic Binoculars or course suffer misalignments quite often --- especially the cheaper ones, which are notorious for poor as-delivered alignment and also tend to lose it easily. And with most binos, drop them and they can of course go way off. About the only ones that can take rough use are the mil-hardened ones, and even there, the USN "Opticalman" Billet guys were servicing them all the time. Your description is Exactly what misaligned binos would do - you accommodate but look away and now must readjust to direct view. So yours are marginal at best and really need servicing. BTW, everyone has some "natural prism" twixt their eyes - which means that All of us are straining just a bit to verge LR. This is quite normal unless it gets to be TOO much and then eye strain or inability to comfortably verge results. This is why binos are always aligned using a good collimator that is big enough to accommodate both objectives at the same time. We had a 29-inch collimator for that at work. Not a cheap Coulter mirror but a custom Ritchey that cost a cool Million! What I LOVE about my Zeiss binos is that the collimation on all of them is downright perfect! You should experience no eye strain using binos. SEND THEM BACK ASAP! Also worth getting your vergence checked by an optometrist - they might do it at no cost and tell you whether your eyes need some "prism." Tom Dey

29-inch Dob in a dome
36-inch upgrade soon
LUNT 80/80 solar scope
FLI 6803 cam
APM 100mm APO Binos
JMI RB-16 Night Vision Binos
Zeiss 20x60 IS binos
Posted 03/27/2015 04:03PM #2
Oh! A follow-up, Robert: The vergence coalignment requirement is Proportional to magnification! So 20x80s MUST be collimated 3 times as well as 7x50s. This really stresses the tolerances on Everything that effects collimation (that center hinge pin used for pupil separation, the alignment and stability of the prisms, etc.) and affects your discomfort! It's really asking a lot of the mechanicals that comprise the binos. that's why the big ones are so temperamental and why the super-high mag ones rely on user-adjustable vergence. The JMI reflective binos (from the 6 inchers to the huge 16-inchers) therefore do (indeed Must!) provide motorized adjustments. Whew! Tom Dey

29-inch Dob in a dome
36-inch upgrade soon
LUNT 80/80 solar scope
FLI 6803 cam
APM 100mm APO Binos
JMI RB-16 Night Vision Binos
Zeiss 20x60 IS binos