Seeing (something much different) with two eyes

For years I have squinted through a telescope with one eye open, one eye closed. This never felt right to me. Now I'm discovering how to observeastronomical objects with one eye working with an entirely different image than the other one has. Here's an attempted simulation using a daylight subject. First, a hawk being chased by a small bird - simulated naked eye view:

Then something close to the magnified view I see with the monocular using one eye.

And finally - and this is just a rough approximation - what the brain tends to do with both images when you ask it to show you both at once.

It's a weird and strangely satisfying experience and my exploration are only starting, but yesterday I extended them – almost accidentally – to include birdwatching. I saw my first osprey of the season circling in a thermal over my backyard and I raised a monocular I was carrying, and out of habits starting to form from telescope usage, I kept both eyes open!

Wow! In my right eye was a magnified image of the osprey that revealed the details of his markings. In my left eye was the osprey and a huge chunk of sky, and trees, etc. And my brain didn't seem to mind these two very different images – it could look at one while relegating the other to a distant, blurry, second level of consciousness, or it could switch and look at the other. It could also process both images at once – giving them equal attention – but I think some detail gets lost when I do this – there's a fuzzy border land where one image merges into and overlaps the other in an uneven way. When I did that it seemed to me I had two Ospreys, one eight times closer to me - the magnification of the monocular – then the other.

Have you tried this? I'm curious to hear from others who have – or are willing to – experiment this way. But let me back up a little. Anyone could try this – the easiest wayis to just use your right eye to look through the left side of a binocular, leaving the other eye open and unblocked.

I read somewhere in the distant past that you should observe with both eyes open because when you close one eye you are raising tension. Open both and the muscles in your face can relax. But trying to observe at the telescope with two eyes open isn't easy. One solution is to wear a patch over one eye. But I've tried the patch and for the most part it bothers me more than closing the eye. It's Just not that comfortable. (Maybe I need to experiment more.)

Then a couple years ago I got on a binocular kick. In fact, when I got back into astronomy with both feet, binoculars were all that I would use. I determined to relearn the sky and reacquaint myself with various deep sky objects by viewing them all through binoculars – very good, vary large, mounted binoculars. And I did so for several months and it was a wonderful experience.

But, of course, binoculars to be really large, powerful, and good are terribly expensive. So I went back to monocular vision until I discovered binoviewers. Binoviewer give you a way to look through the telescope with both eyes by using a device that splits the light emerging from the eyepiece into separate paths for each eye.

Essentially this is still a cyclops operation. Funny. You have light coming in one large "eye" – the telescope lens or mirror – then you split it and send it to two eyes, each with a dedicated eyepiece – then you ask your brain to put the two images back together again. Well, our brains do that all the time since we have two eyes, so it's a natural task. I like this approach – especially when viewing the moon. I also find it more relaxing because both eyes are open. But binoviewers are not binoculars. They offer some advantages and some disadvantages that have been frequently explored in various articles.

But then I got this idea – for various reasons – of using a small telescope on a parallelogram mount meant for binoculars – but using it "straight through." That is, you remove the typical diagonal and just as with the binoculars, you look up when viewing the sky – but you have only one telescope to look through instead of the two the binoculars offer. What's more, you do this while comfortably seated in a chair with an adjustable back – no neck strain.

Now as soon as I started looking up to this sky this way – with only one telescope in front of me – it semed natural to open both eyes. For one thing, this gives you a tremendous sense of place and erases some of the reality gap that inevitably develops as you use a telescope. You look at the Orion nebula with one eye – and you see Orion and neighboring constellations with the other. And as withy the osprey, you can go back and forth. My right eye takes the magnified view usually – my left eye lives with the everyday reality of the limitations of our vision. As with the osprey, you can keep both eyes open, but let your brain assign priority to one so that, for example, image dominates and is clearly seen and the other falls into a sort of peripheral vision category. Or you can give priority to the image through the naked eye.

Or – and this is what I find most fun – you can let both eyes do their thing. When I do this I frequently see the telescope tube and part of the mount with my left eye, as well as the sky beyond – but my right eye overlaps the vision of the cluster or nebula or whatever and magnified stars or gas clouds seem to be sprinkled over the telescope tube. Cool!

How much of this can I take? I don’t know. Is it really the way to go? I don’t know. But when I lifted the monocular up yesterday I suddenly realized I have a tool with which I can explore this concept any time. This is not a toy. This is an 8X32 monocular with a 7.8-degree field (that's wide) and an incredible 2-foot short focus. It's good and it's versatile – and Orion has been selling them for a couple years for about $140. (Not inexpensive!)

But I like being able to toy with this concept in the daylight. (Observing time on clear nights is limited and precious and there's only so much experimenting with equipment and techniques that I want to do then.) I want to see if this is simply something you have to get used to – or if, in getting used to it and using it too much , you give yourself a headache as you do when using binoculars that are out collimation.

Meanwhile – your thoughts? Your experiences? Email me and I'll be happy to share them by posting them here.

Comments? Please send to gstone@umassd.edu