Telescope Binoviewers: 5 Things To Know

When it comes to amateur astronomy, there are plenty of different things that you need to get used to. For one — you can’t view a telescope with both eyes. And yet, seeing as humans are so used to observing with both of their eyes, using a telescope can seem irritating and tiring for your eyes at first.

However, there are plenty of ways to mitigate any misgivings that you might have regarding the use of telescopes — such as using binoviewers!

If you’re unsure of how these devices work, we’ll tell you everything you need to know right here.

1. Here’s what a telescope binoviewer is

A binoviewer is a telescope accessory that lets you use both eyes with only a single objective. It has two main components: a beam splitter, which splits the incoming image into two fainter but identical copies, and mirrors/prisms that send the images to two identical eyepieces.

By the way, binoviewers are an essential part of laboratory microscopes, too. If you’ve ever taken a lab science class, then you’ve most like experience a sort of binoviewer, whether you realized it or not! 

2. The main reasons to use one

While there are many specific reasons why you may consider using binoviewers as an amateur astronomer, there’s one crucial reason that’s the main thing here — when you’re using a classic viewing lens in a telescope, you can only look at the sky above with one eye at a time. This is something that beginner astronomers are simply not accustomed to; over a single viewing session, it’s easy to develop eyestrain and fatigue. That’s where a binoviewer comes in — allowing you to turn this into a double vision for both eyes.

Now, binoviewers can give you immensely stunning views of deep-sky objects, as well as nearby planets and the Moon. However, you need to remember that binoviewers also require you already having at least one eyepiece to go with it. Picking the best one is essential to having the best possible experience while stargazing.

3. How binoviewers differ from binoculars

In some cases, you will find that certain characteristics of binoviewers are the same, or different compared to binoculars. Here, we’ll outline some of the common traits and main disparities. Fist of all, the most important thing to remember about binoviewing is that it’s better tuned to how human brains perceive visual information; in a way that’s far more natural compared to single-eyed viewing. 

This is something that both binoculars and binoviewers have in common — lending more credence to the popularity of binoculars when it comes to amateur astronomy. Another thing that binoviewers and binoculars have in common is that people often find that distant starfields or objects almost seem three-dimensional.

However, the objective’s narrow spacing means that binoviewers and binoculars do not actually give you real depth perception; what you see is merely a trick of the brain. There’s another effect that both of these pieces of hardware have in common — like the fact that some subtle details in closer objects are better visible with binoviewers and binoculars compared to regular telescope eyepieces. The reason for this is that the brain gets the same set of information from both of your eyes, allowing it to spot more details. Finally, the fact that you can relax far more when using binoviewers and binoculars compared to single-eye view lenses is also apparent. 

On the other hand, there are plenty of ways that binoculars and binoviewers differ. For one, binoculars have no floater suppressions, while binoviewers do. These “floaters” are actually small pieces of organic matter that are found inside the human eyeball’s fluid. If you’ve got binoviewers with small exits, this can be awfully distracting — if not for the fact that binoviewers cancel out the effects of the floaters, while binoculars don’t. 

Also, plenty of observers notice astigmatism as a factor with small exit pupils; however, this is something that telescopes can easily cancel over the course of processing. And there are some factors that aren’t as technical. For instance, if you want to have setups with bigger apertures, it’s far simpler and less costly to do so using binoviewers compared to binoculars. You can always adjust your magnification levels by messing around with different eyepieces, or even by utilizing focal reducers and multipliers. 

4. Some important drawbacks to understand

While binoviewers provide plenty of comfort and some advantages to their users — there are also certain issues with them that you should keep in mind. You’ll find that one of the more obvious downsides to using binoviewers for astronomy is the added expense. Obviously, if you want to properly make use of binoviewing in your telescope, you will have to double the size of your eyepiece collection. There are certain contemporary systems which manage to minimize this by allowing you to adjust the magnification in a single eyepiece; this reduces the amount of different eyepiece pairs that you need, also making every one you already own more valuable. 

On the other hand, one of the other drawbacks is the fact that binoviewers tend to split your light into separate and distinct two paths. And when you run that through additional optical equipment, less light will end up reaching both of your eyes than you’d receive with one-eyed viewing. Now, plenty of users will tell you that this is balanced by the better image processing efficiency your brain can reach with two eyes — but it’s still worth noting. 

5. The most important features to look for

Naturally, while you choose the best telescope binoviewers, you will have to consider certain features before you make your purchase. For one, you need to remember that these are essentially two eyepieces that you’re pairing up. Considering that, these two need to be completely in sync with each other. That means that their optical characteristics much match completely — which includes their field of view, exit pupil size, and focal length. 

If you’re looking at the ideal case, you want both of these eyepieces to be identical — with the same manufacturer, same focal length, and overall the same design. Remember, as close as you manage to produce two identical images with these eyepieces, your brain will have less trouble merging two of those images into a coherent one. 

Also, you should know that while there are some expensive eyepieces out there — binoviewing pairs are far less costly than they once were. You can find imported units that provide a decent performance for no more than a couple of hundred bucks; which used to be an imaginable bargain a couple of decades ago. 

Wrapping Up

At the end of the day, there are both advantages and drawbacks to using telescope binoviewers. But if you’re someone who’s just beginning to foster an interest in astronomy, know that this kind of astronomical tool will be essential to reducing your levels of eye fatigue and general strain!