Consider the Monocular

[HenryC]

If you're interested in buying a pair of binoculars, it might be worth your while to consider a monocular instead. A monocular is essentially half a binocular, or a binocular sawed in half. You use it like a small telescope, or a spyglass.

Binoculars have the advantage that both eyes are used, and the brain integrates both images together, allowing you to see finer detail and fainter images for a given level of optical quality. But the disadvantages are also considerable.

Binoculars fail to provide this enhanced performance unless the two halves are spaced and focussed for both your eyes, a time consuming procedure that must be learned and practiced, and frequently repeated, and one that depends heavily on the mechanical design and construction of the binocular and how well they are aligned and matched. Needless to say, optimizing these mechanical considerations add to the cost of the glass without improving its optical performance in the slightest.

Since for most applications, a glass is used quickly, the ability to quickly bring it to bear on its target is often more critical than optimizing the image to perfection. For use in sports, marine, or nature study, you may simply not have the time to be fumbling around with adjusting differential focus and inter-pupillary distance. In some applications, like astronomy or surveillance, binoculars are superior because of their optimal image-forming performance, and because time and convenience are not critical. But even by the telescope, sometimes you just need a quick look to familiarize yourself with a star field, and the monocular works better.

Because of the increased weight and bulk, binoculars are more of a hassle to carry in the field, harder to hold steady, and usually require both hands. Monoculars are lighter, more robust, and cheaper than similar quality binoculars, although the value may be less. A monocular has half the materials, half the optics, and has far less matching, alignment and mechanical issues at the factory, but they don't cost half as much as optically equivalent binoculars. I suspect the ratio is closer to 3/4. So don't let price alone influence your decision.

When I was a pre-teen, I bought a 7×50 monocular for astronomy. It was the perfect instrument and I still have it! I use it now primarily as a night glass for marine use because of its wider field of view and stability on a moving platform. My aged pupils don't dilate as much in dim light as they used to and can't take advantage of the full light cone in dim light, so for all-around use I now prefer a 10×50 binocular.

But the latter is a pain to carry around and use for nature study, concerts, or to sporting events, so I have just ordered a 10×50 monocular. There is no sense in owning a toy if it is just too much trouble to take along with you.

[jthatcher]

hi Henry,
  thanks for taking the time to share your thoughts on a monocular..  in fact, i have been cross-eyed since i was 4 years old..  never figured out what happened, but it really doesn't matter - my brain never coordinates or merges  the two images from my eyes - i only use one at a time, so  i essentially use my binoculars as a monocular anyhow!   

   i have a friend who operates on eyes, and he told me that he could straighten out my eye, but when he described the procedure and then told me that i would never have binocular  vision anyhow -  i wanted nothing to do with it      i will check out the monoculars later this evening..  jt

[Shawn]

Henry,

For awhile there was a guy on ebay selling half of Fujinon 7x50 binoculars that had snapped in two. They were very inexpensive... $20 or so. They were fixed focus so each half had the eye adjustment in it. I picked one up and it is helpful. In some ways it is easier to keep steady than binoculars. and it is very handy to hand to the kids as they can immediately use it and hold it.

At night I find it harder to use though as I loose the depth perception advantage of binoculars.

Shawn

[HenryC]

Dear Hatcher

I'm no doctor, but I'm not quite sure you wouldn't be able to use binoculars after your surgery..  You might want to consult with your physican friend on this.

In my understanding, "binocular vision" means your eyes cross slightly, naturally, in order to help you judge distances to nearby objects.  This is why its easier to thread a needle if you use both eyes.  At least, its easier for me!  With binoculars, you are looking at objects "at infinity"  so your eyes don't need to cross, they are parallel, looking in the same direction.  After your surgery, you might be able to use binoculars just fine.

I'm kind of familiar with this because I used to cross my eyes for a living!  I was a photogrammetrist, a stereo plotter operator.  I used to look at overlapping pairs of aerial photographs through a complex binocular machine in order to draw 3D contour maps of the ground.  This required using my depth perception and I was trained to do this to a very high degree of precision. 

As a result, I learned I had a minor vision defect; my eyes would not properly cross, one was a little weaker than the other and the two vision points would not merge in one plane; one slid under the other.  It was not an issue in normal life, but doing this kind of work it made a big difference.  Special glasses were made for me so I could work, but they didn't help much, and eventually I just had to compensate mentally to correct for the problem.

At any rate, don't give up on the binoculars just yet, and when you decide to buy your equipment, feel free (or anyone else reading this) to ask how to select a bino/mono for your particular application.  For marine use, a 7x50 is optimal, but you may have other things in mind as well, like sports or nature study. I used to have an article here on how to select binoculars, but I had to remove it when I got it published.  If I can locate it, I'll post it again.

[HenryC]

Henry,

For awhile there was a guy on ebay selling half of Fujinon 7x50 binoculars that had snapped in two. They were very inexpensive... $20 or so. They were fixed focus so each half had the eye adjustment in it. I picked one up and it is helpful. In some ways it is easier to keep steady than binoculars. and it is very handy to hand to the kids as they can immediately use it and hold it.

At night I find it harder to use though as I loose the depth perception advantage of binoculars.

Shawn

I never noticed any depth perception with binoculars, its still flat for me, but binoculars do give a clearer, sharper, brighter image than a monocular.  The problem is that its such a hassle to get both of them focussed perfectly for each eye, and keeping the two halves centered on each eye is a problem.  In cheap binoculars, every time you adjust the distance between the tubes, it throws the focus out in one or both. If you're on lookout duty, you can take the time to balance the two halves perfectly, but for a quick look-see at an ATON or another boat, you generally wind up closing one eye and using the other.

You got a bargain on that Fujinon.  The Hawke 10x50 monocular I just ordered set me back $80, and I won't know the quality until it comes in the mail.

[Shawn]

"I never noticed any depth perception with binoculars, its still flat for me,"

Really? For me they dramatically enhance depth due to the wider interoptic distance.

"In cheap binoculars, every time you adjust the distance between the tubes, it throws the focus out in one or both. "

Yes, that is a pain in cheap binoculars. I have Nikon "Sport and Marine" binoculars. They are nice because they are not central focusing so they avoid that problem. Once each eye is dialed in your focus is fixed and doesn't need to be adjusted. Makes it easier to use them at night. On the flip side it means they can't really close focus compared to central focusing binoculars.

Shawn

[crazycarl]

I've been using a monocular for years now.  I keep both eyes open while using it, thus I can scan ahead and not lose site of what's right in front of me.  Very important when your sailing in crowded waters.

[HenryC]

I've been using a monocular for years now.  I keep both eyes open while using it, thus I can scan ahead and not lose site of what's right in front of me.  Very important when your sailing in crowded waters.

In astronomy you always observe with both eyes open, to reduce fatigue, but its easy because its dark.  I've never tried it in daylight!

[jthatcher]

hey guys.. lots of good info -  it is interesting to hear you all talk about depth perception - because of my condition,  i don't have any.  the brain does compensate,however, so i have what is called "learned depth perception"    i can still drive,  and dock the boat    but it did keep me out of the Navy     and it was pretty scary trying to land a glider a few years ago when i took some flying lessons..    i would never qualify for a pilot's license, but you don't need the faa physical for gliders      however, I can't afford two hobbies, so i gave up the flying idea when i bought the boat!    The Doctor told me that if i had had surgery right when my eyes crossed I might not have any problems, but after all of these years, the brain simply would not adjust...   oh well.   looks like it is time to order a monocular!   i will wait for henry's review of the one that he got   jt