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Astigmatism and binoculars

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#1 jaketbone

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Posted 17 October 2013 - 10:00 AM

Hello, I own a pair of FUJINON 10X70's and experience some astigmatism. I was wondering if using 16X70's would reduce some of that. FWIW, I am a 59 y.o. male living in the Wash DC suburbs. My eye DR mentioned that my right eye is precataract and the lens is a little yellowish when examined. I have orange skies even under the best of conditions. I have put on my computer glasses (single vision) and they seem to help. When I use the Dioptrix on my telescope, I find that over the span of the night that the astigmatism will go away.
Any thoughts?

#2 KennyJ

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Posted 17 October 2013 - 11:40 AM

Leaving the glasses to one side, you could try making / fitting some masks to the 70mm objective lenses to see how much difference it makes.

Around 44mm with the 10x magnification should more or less replicate the exit-pupil diameters of the 16x70, although the effective increase in focal ratio may provide an added bonus, thus possibly raising your hopes unduly high for a straight switch to a 16x70.

If you end up wearing glasses to improve the situation, as I do, then the very short eye-relief of the 16x70 will restrict the field of view, possibly quite dramatically.

Kenny

#3 daniel_h

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Posted 17 October 2013 - 04:37 PM

i have astigmatism (i mostly need glasses to view naked eye stars), but the smaller the xit pupil the beter the viewing, so the 16x70's would help a little, but xit pupil will still be 4.4ish as opposed to 7
I pesume you're asking about using the bino without astigma correction - otherwise just ue the 10x70 with glasses on & t should be right. i have thin glasses so could view thru the 16x70, most glass lenses are thicker & have some restriction of the view

#4 Erik Bakker

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Posted 17 October 2013 - 05:12 PM

Reducing exitpupils will have a great positive impact on the effect your astigmatism has on the (perceived) image quality of stars.

For my eyes, with 3mm exitpupils sharpness will hardly suffer, 5mm is a good compromise between sharpness and brightness, while 7mm will show a very bright image with significantly reduced star-sharpness.

So to your eyes, I am quite certain that the 16x70's will present sharper stars in a less bright image than the 10x70's.

In closing, I had trouble with the sharpness of stars with the 7.1 mm exit pupils of my Zeiss 7x50 B/GAT, but find the 6 mm of my Zeiss FL 7x42's already delivering acceptable sharpness with a very bright images. But it is nowhere near the super sharp stars in my 3.2 mm exit pupil Zeiss Fl 10x32's. Those little binos show superb sharpness over a very wide field similar to a longish focal length panoptic in an APO refractor. Truly stunning for stuff like the Pleiades under clear dark skies!

#5 GlennLeDrew

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Posted 17 October 2013 - 07:09 PM

I have ~0.75 diopter of astigmatism, which by good fortune has the same orientation in both eyes. With virtually every bino I've ever used, I find that I can find a sweet spot where eyepiece astigmatism nicely cancels my own. That my astigmatism causes a horizontal smearing, I place my target either above or below the field center by about 1/4 to 1/3 the distance from center to edge, and obtain a very sharp image for critical examination.

If the exit pupil goes below about 3-3.5mm, astigmatism is not a problem worthy of compensating.

#6 faackanders2

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Posted 17 October 2013 - 08:14 PM

I have ~0.75 diopter of astigmatism, which by good fortune has the same orientation in both eyes. With virtually every bino I've ever used, I find that I can find a sweet spot where eyepiece astigmatism nicely cancels my own. That my astigmatism causes a horizontal smearing, I place my target either above or below the field center by about 1/4 to 1/3 the distance from center to edge, and obtain a very sharp image for critical examination.

If the exit pupil goes below about 3-3.5mm, astigmatism is not a problem worthy of compensating.


I thought you used ethos eyepieces for you home made binos. Couldn't you use dioptrix with those for perfect astigmatism correction.

#7 SMark

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Posted 17 October 2013 - 08:27 PM

Reducing exitpupils will have a great positive impact on the effect your astigmatism has on the (perceived) image quality of stars.

For my eyes, with 3mm exitpupils sharpness will hardly suffer, 5mm is a good compromise between sharpness and brightness, while 7mm will show a very bright image with significantly reduced star-sharpness.


Well, thank you! This answers a big question of mine that came up just recently. I have astigmatism in my right eye that has gotten worse as of late. Still, I am able to tolerate it just fine with my Canon IS models, my 16x80, my 30x80, and even my super wide 7x35s. But my 7x50 super wide and my 6x42 SARD have really frustrated me, and I found myself constantly fiddling with the right diopter. Since the SARD does have quite a bit of eye relief, I decided to try it with my glasses on, and what a huge difference this made. Now I understand why. So I've decided that this is the only way I'm going to observe with the SARD from now on. My super wide 7x50 is likely to not get much use though, since its eye relief is so short. But that's okay, the SARD is so much better anyway...






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