Is it my binoculars or my eyes??

[RobH2020]

Hi all,

I seem to have a problem with looking through binoculars. I can never resolve the image provided by both eyes into one image - I can always see two images slightly offset, so nothing's ever completely clear.

Do you know what the problem could be here?

I originally thought it was my interpupillary distance, when i got some Astromaster 15x70 the IPD was much too big for my narrow eyes. But now i've got some  Opticron Adventurer 10x50 with an IPD that in theory suits me. Yet I still have this issue!

Can anyone fill me in on what might be going wrong? 

Thanks! 
Rob

[Peter Drew]

I think it's a real but frustrating issue that some people just don't get on with binocular vision, be it binoculars or binoviewers.  You have already tried the obvious experiment, adjusting the IPD as this is often the problem.  I can't think of any further advice unfortunately.      ☹️

[Stephenstargazer]

If you have this problem with all binoculars then it could be that your brain is unhappy to bring the two images  together. I get this sometimes with star fields and find a few good blinks and relaxing my eyes normally lets them merge.

If you have the problem with terrestrial views then the two halves of the binoculars are probably out of collimation. Get someone else to try the binoculars and see if they agree? The prisms or eyepieces in the binoculars have to be reset. Opticron service is (or were!) pretty good if you have a problem.

Good luck!

[Rusted]

Checking binocular alignment is fairly easy if you can rest them on something solid.
A tripod with binocular adapter is probably safer than resting on a post or a wall.
Focus the binoculars on a distant object at roughly your own viewing height. [Horizontal.]

Get any dark card [playing card size] and wave it quickly from side to side in front of the bino objectives.
You can wave your hand back and forth but risk knocking binos off an unsafe rest!
The card will block your view through each side of the binocular in turn.
If the image "jumps" back and forth then binocular alignment is likely your problem.

I discovered my Zeiss 10x50 Jenoptem were out of alignment from new.
I fixed the problem myself by rotating the wedged rings in front of the objectives.
They have since stayed in perfect alignment for the last 30 years.
Before that they would make me queasy within a minute of trying to view through them.

You could test your own naked eyesight using a card while staring at a fairly distant subject.
You may have astigmatism in one eye which spoils your eye's natural binocular vision.
Just a guess.


 

[RobH2020]

52 minutes ago, Rusted said:

You may have astigmatism in one eye which spoils your eye's natural binocular vision.
 

Ah, I do have astigmatism and wear glasses to correct for that (as well as short-sightedness). Is that an issue when it comes to using binoculars without wearing my glasses?

[Rusted]

33 minutes ago, RobH2020 said:

Ah, I do have astigmatism and wear glasses to correct for that (as well as short-sightedness).

Is that an issue when it comes to using binoculars without wearing my glasses?

Almost inevitably. Your glasses will have individual power correction and for the astigmatism in each eye.
Remove your glasses and you have instantly lost the individual eye compensation.

Careful focusing of each eye helps with the power issues but [probably] not with astigmatism.
Most binos have individual eye correction. Or both, plus one EP with adjustable, diopter correction.

Many modern binos have fold down eye cups to allow glasses wearers to enjoy the instrument along with their prescription glasses.
A chat with your optician about bino use might be helpful. It must be a very common problem.
Some binos and binoviewers can have compensating lens attached to the EPs. I have read about this on the astro forums over time.
These lenses would only need to correct your astigmatism. Any power differences can be corrected by focusing and diopter adjustment.

[Merlin]

I have double vision, due to a muscle having relaxed in the right eye. It’s quite severe, so I wear specs to correct for the problem. This meant that I couldn’t use some of my binocular collection because  they didn’t have enough eye clearance for specs.

 

I solved the problem by using the lenses from some of my spare specs. I removed the lenses , then sawed and filed them down so that they could be fitted and glued into the eyepiece cups. Where there’s a will ... .

 

[RobH2020]

14 hours ago, Merlin said:

I have double vision, due to a muscle having relaxed in the right eye. It’s quite severe, so I wear specs to correct for the problem. This meant that I couldn’t use some of my binocular collection because  they didn’t have enough eye clearance for specs.

 

I solved the problem by using the lenses from some of my spare specs. I removed the lenses , then sawed and filed them down so that they could be fitted and glued into the eyepiece cups. Where there’s a will ... .

 

wow good solution!

[RobH2020]

16 hours ago, Rusted said:

Almost inevitably. Your glasses will have individual power correction and for the astigmatism in each eye.
Remove your glasses and you have instantly lost the individual eye compensation.

Careful focusing of each eye helps with the power issues but [probably] not with astigmatism.
Most binos have individual eye correction. Or both, plus one EP with adjustable, diopter correction.

Many modern binos have fold down eye cups to allow glasses wearers to enjoy the instrument along with their prescription glasses.
A chat with your optician about bino use might be helpful. It must be a very common problem.
Some binos and binoviewers can have compensating lens attached to the EPs. I have read about this on the astro forums over time.
These lenses would only need to correct your astigmatism. Any power differences can be corrected by focusing and diopter adjustment.

Aha thanks, I'll have to look more into binocular use for those with astigmatism...

[BinocularSky]

18 hours ago, RobH2020 said:

Ah, I do have astigmatism and wear glasses to correct for that (as well as short-sightedness). Is that an issue when it comes to using binoculars without wearing my glasses?

Could be; I have astigmatism; different axis in each eye, and it takes my eyes a few minutes to re-merge images when I remove my glasses. Irritatingly, it gives me "step" (vertical displacement) which is the worst kind of misalignment.

 

[Stephenstargazer]

10 x50 have 5mm exit pupil so even mild astigmatism will be noticeable. Opticron say these bins have 19mm eye relief which is supposed to be enough to wear glasses with them - depending a bit on how glasses fit on your face. You might try taking the eyecups off?

An expensive possibility is to use astigmatism corectors made by TeleVue for eyepieces, provided they could be fitted instaed of the rubber eyecups. Look here for some advice:

https://www.televue.com/engine/TV3b_page.asp?id=87

[Robindonne]

Noticed some moments the same problem.  I have no glasses or other eye issues as far i know. It happened once or twice.  Dont know if its because, by the time i use bino’s, my eyes have been active for 16+ hours.  

[GrumpiusMaximus]

I have a slight astymastism too and it does sometimes cause issues, especially seeing as I find viewing with glasses on very uncomfortable.  I frequently find the diopeter adjustment maxed out as well due to the different prescription of each eye, which are a few steps out from each other (short-sighted).  I need to do some experimenting but I think a bino hood is in order so that I can keep my glasses on, roll up the eyecups and get everything focussed properly without any extra light coming in...

[Carbon Brush]

Something not mentioned, though I may have missed it.

Are any of you fellow specs wearers using varifocal lenses?
A varifocal lens is quite a compromise lens at the best of times, even more when astig correction is brought in.
If you don't look through quite the right part of the lens, you get distortions.
Thats why they take a bit of getting used to and some people never adapt.

I generally find it best to use scopes and binos without specs. Contact lenses fix the astig.

Having said that. If 'not quite right' varifocals or other lenses have been pulling your eyes off axis for a while, it takes time for them to recover.
This can (from my experience) take seconds, or minutes, or even hours.
 

[banjaxed]

I have no problem with terrestrial viewing through binoculars but I was very disappointed when I bought some binoviewers as they just didn't suit me at all. 😞

[John]

I get on fine with binoculars but not with binoviewers, unfortunately

I've owned 2 or 3 of the latter items but found that they were just not "my cup of tea" so let them go to new homes.

I've no explanation as to why this is though

This ought to have been a wonderful observing experience

[Carbon Brush]

I have found that in daytime I can pull together a double image whether caused by bad/tired eyes, or poorly collimated binoculars.
However, at night my brain has problems working out how to pull eye muscles to align stars.
I reckon it is the difference between two solid day images, and 'join the dots' at night.
Just my completely uneducated and ill informed guess😁.

Opticians don't always get it right though. It is always worhwhile running a good check on new specs.
I once had a pair of specs that just didn't feel right. But I couldn't work out why. They just felt like hard work.
After a couple of weeks of struggling, one night I changed between nothing, old specs, and new specs, to try to work things out.
With new specs, I looked at the moon. Nice clear image, but not a relaxing view.
Without specs or with old specs, I looked at both moons 🌙 🌙 and watched them merge into one 🌙 over a few seconds. Without 🥂🍻 booze!
Once the moons had merged, the view was relaxing. Though of course blurred without specs.
The optician had incorrectly prescribed a prism (up/down) correction to one eye.

[Paz]

My eyes are not level and it took me literally years of problems with binoculars and binoviewers before I finally worked it out. If I keep both eyes open and using my hands cover them alternately, a distant object looks high/left to my right eye and low/right to my left eye. In collimated binoviewers I see the same thing and initially thought it was the binoviewers.

If I level bins or binoviewers in front of my face and then look through I get a misalignment problem. But if I focus on the exit pupil from a few inches back and make sure they look level then the views are good despite the fact that if you look at the binoviewer itself it no longer looks level.

Another problem I discovered is my glasses were not square to my face, so if I rested my glasses on the binoviewers (thinking that would be square) in fact it meant my head was not square and my eyes were looking slightly to the side. I fix this by again hanging back and picking up the exit pupils and ensuring they both look the same size before I go up to them to view. If they look different sizes then one eye is closer than the other.

The last thing I do is just before moving up to the eyepiece to view, get my eyes focused on the target/infinity, as my natural inclination is to focus on the eyepieces and then my eyes have a fit adjusting to infinity and also keeping alignment.

[ollypenrice]

On 16/04/2021 at 20:21, banjaxed said:

I have no problem with terrestrial viewing through binoculars but I was very disappointed when I bought some binoviewers as they just didn't suit me at all. 😞

Same for me. I'm fine with binoculars but prefer monocular observing with a telescope. I find binoviewers add complexity in terms of getting everything just right in terms of position, diopter, etc and then don't add anything when that's done.

The OP might simply find that a monocular rather than binoculars worked better for him?

Olly

[Astrobits]

Talk to your optician about your problem. My local optician ( part of a well known chain) never mentioned prism when checking my eyes. It wasn't until I asked them to do it did the prescription include a prism correction.

I have always known that I had a slight prism error which had been mentioned many years ago during an eyesight test ( back then the optician called it "wedge" ). It has never bothered me in normal life but when using any binocular instrument ( Binoculars, microscopes etc. ) It was much more apparent.

Nigel