eye position for binoviewers and binoculars

[Paz]

I've been getting the hang of binoviewers for some time and a few realisations have dawned on me in this time about problems with me rather than my astro equipment. I am interested in whether others have any similar experiences.

If I take a collimated binoviewer (or binocular) and hold the eyepieces exactly horizontal/level a few inches in front of my eyes then the right image looks like it is slightly higher than the left, and at the eyepiece the right image looks higher than the left.... but then if I ignore whether the binocular looks physically level and focus on the images and make them look horizontally level from a few inches out then at the eyepiece the images (and field stops) look level... but then stepping back the binocular is actually tilted slightly - with the right side down.

Setting aside any optics, if I just look ahead and blink my eyes open/shut alternately the same thing occurs - the image appears slightly higher from my right eye.

I don't know what the why's and wherefores of the above are, but from trial and error I know if I start a few inches back from the eyepieces, make sure the separate circles/images are level and even, then move up to the eyepieces at which point they are merged, and then ignore the fact that it feels wrong and focus on the fact that it looks right, then all is well. If I just go straight up to the eyepieces and go for a position that feels correct/symmetrical either by the way it feels on my face/glasses or even by looking for a good and even field stop all round in each eye, I end up with the right image looking high. 

I've also discovered that my glasses do not sit squarely on my face - this doesn't matter for cyclops but for bino it has meant that whenever I rest my glasses on the eyepieces in fact my whole face is turned very slightly to one side. I am not looking squarely ahead and my glasses are not quite square to the eyepieces, this is something I need to fix.

[Peter Drew]

I have a similar problem.  According to my optician, I have a slight eye muscle issue which drops one my eyes slightly relative to the other.  Like you, I can address it by tilting my head.  I have to be careful to allow for this when collimating binoculars for others!.       🙂  

[Paz]

2 hours ago, Peter Drew said:

I have a similar problem.  According to my optician, I have a slight eye muscle issue which drops one my eyes slightly relative to the other.  Like you, I can address it by tilting my head.  I have to be careful to allow for this when collimating binoculars for others!.       🙂  

Thanks for the reply, like you I found if I tilt my head slightly over (left side down) that also solves things. I thought I was going a bit mad though as I've never come across any commentary on this issue before.

I've been adjusting the collimation of my binoviewers thinking I could improve on it but in hindsight I think it was good all along and I just hadn't realised my eyes were a bit wonky.

[wulfrun]

I also have this problem - caused by cumulative damage to one of my eye-muscles, from migraines, over many years. It has some fancy name that I think was a "latent squint" (double vision). If I close my eyes alternately my "view" shifts alternately but with both eyes open my brain forces them to look at the same point (mostly). I find it worst when trying to view through an eyepiece of some sort whilst also seeing with the other eye, such as using a camera with both eyes open. I've learned to live with it. I don't think it's uncommon, although in my case the cause is very rare.