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How to Select Binoculars for Astronomy

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Binoculars - The Best First Astronomical Instrument



If you're like me, you 've often noticed bright stars, formations of stars, and when away from city lights, the breathtaking Milky Way. For some of us, the wonder sticks, and we want to see more. Of course, while naked eye astronomy is enjoyable, putting some kind of lens between your eye and the stars enhances the experience considerably. And the simplest and cheapest optics you can apply to astronomy (and you may have such optics already in your closet) is a pair of binoculars.

Yes, it's true, you can enjoy a lot of astronomy with nothing more than a pair of binoculars. In fact, if you're new to the astronomy hobby, binoculars is definitely the least expensive way to get started. If you want a guide on how to get into binocular astronomy, consider Touring the Universe through Binoculars: A Complete Astronomer's Guidebook (Wiley Science Editions). This book will give you a big nudge in the right direction. Add a pair of binoculars, and you're on your way.

I essentially started with binocular astronomy (well -- monocular astronomy). I was probably not yet in high school when my parents bought a little 7 power 50mm diameter telescope on a table-top stand. I think it was called a Moon Watch telescope. It was modest in size, but the optics in it were excellent.

That little instrument was my first telescope, and I went out often to look at the Moon, Jupiter, and rich star fields.

The Moon was tantalizing, with a few prominent craters and mountain ranges visible, and many details just beyond reach.

Jupiter was just a bright object, but the tiny Galilean moons could be easily seen.

And sweeping the little telescope through the Milky Way was always an adventure. I could actually see the Milky Way with my naked eye in those days from my small town backyard.

That little telescope was basically 1/2 of a pair of 7x50 binoculars, yet it kept me spellbound for a year of two. It eventually became a finder scope on an 8" Dobsonian telescope.

A good piece of equipment to begin your astronomical journey would be a quality pair of 50mm binoculars, preferably with not more than 10 power. A good example is this Bushnell PowerView 10x50 Wide Angle Binocular. I also commonly use a pair of 15x70 binoculars, much like the Celestron SkyMaster Giant 15x70 Binoculars.





Binocular Basics

Binoculars are basically two telescopes mounted side by side, and aligned so that one can look at a distant object with both eyes. Binoculars use prisms in both barrels to deliver an upright image to the user.

The most common binoculars use what's called porro prisms, and lead to a binocular with objectives offset from the eyepieces. Roof prism binoculars, more compact, look literally like two straight through telescopes mounted side by side.

Compact is nice, particularly for much daytime observing. But just as with telescopes, binoculars with bigger diameter lens show more.

Having said that, let me add caution. Low power binoculars are great for taking in comets and sweeping star fields, and can be simply hand held. But it gets pretty difficult holding binoculars that are too large -- and heavy.

Shown in the above image are two pair of 50mm binoculars. That means the business end of each instrument (pointing at you in the image) has objective lenses of 50mm diameter.

While these two binoculars look virtually the same size, they are actually somewhat different. The one on the left is a pair of 7x50s, and the other is a pair of 16x50s.

Binoculars are commonly listed by their magnification, then their diameter. So the 7x50 left pair magnifies 7 times, and has objectives of 50mm diameter.

The pair on the right (16x50) magnify 16 times, and are also 50mm in diameter.

"Which is best?" you are probably asking. In truth, for hand-held astronomy the 7x50s are better. Why? Because it turns out to be quite difficult to hold anything magnifying over 10 times steady enough to useful.

So I can easily hand hold the 7x50s, but the 16x50s really need to be tripod mounted.

I show these because I recommend that for astronomy, you start with a pair of 7x50s. It's really incredible what you can see with them.

If you have something smaller, say 35mm or 40mm diameter ones, by all means give them a try. You'll be surprised by what you can see. But you can see dimmer objects with 7x50s, and they are can be had for less than $100. You can certainly pay more, and get better quality to boot. But even moderately inexpensive ones perform very well. Just avoid the least expensive unless you can actually look through them before buying.



Bigger is Better?

This image shows the 7x50s beside a much bigger 15x70 pair of binoculars. Recall that 15x70 means the binoculars magnify 15 times, and have objectives of 70mm (nearly 3 inches).

I must tell you that when I first saw the 15x70s, they made my mouth water. And when pointing them to the sky, I wasn't disappointed. The Moon is rather spectacular through the 15x70s. The Andromeda galaxy is better viewed with them than with my telescopes.

But recall that anything over 10 power simply doesn't provide steady views when hand held. I've tried propping my elbows on the cab of my pickup, leaning against the corner of my workshop, all manner of bracing. In the end, the 15x70s really only work well when on a tripod.

So what am I saying? I guess that while I love those 15x70s, I really wouldn't suggest that you start with something that large.



The Big Binocular Tradeoff

Here's another view of the 7x50s and the 15x70s. In this view, you can clearly see the considerable difference in their sizes.

Now you can get a hint of the increased fatigue you'd get swinging a large pair of binoculars around for a couple of hours, versus a more manageable pair of 7x50s.



What Can You See with Binoculars?

So, what can you see with binoculars?

The answer: A lot!

With a moderate sized pair of binoculars you can see some of the major features of the Moon.

In fact, a pair of binoculars is a wonderful way to watch a lunar eclipse. NOT solar eclipse -- NEVER LOOK AT THE SUN WITH BINOCULARS. Next time the Moon passes into the Earth's shadow, plan to watch it with your binoculars. You'll see the Earth's shadow creep along the face of the Moon, notice features that were clear as a bell minutes before virtually fade away. Then, if you stay with it, you'll see those features re-emerge later in the evening (or early in the morning).

You can see most of the Messier objects, though admittedly many will look like just another star. But some of the galaxies, a few nebula, and most open clusters will be very enjoyable. There are also many similar objects listed in other star catalogs such as the Caldwell catalog and the Hershel 400, so the total number of targets is in the hundreds.

I particularly like the Pleiades and the double cluster in Perseus through binoculars. And my best views of comets is usually through binoculars.

Celestial events, especially involving the moon, are wonderful through binoculars. As the moon moves through the night sky each evening, it often passes near or through some heavily populated star fields. These events are always pleasing.

You'll be able to check on Jupiter's 4 biggest moons and see their relative positions change night to night. At times you'll see less than 4 as others are either behind the planet or lost in the planet's glare.

Sweeping through the Milky Way, you'll find many rich star fields that are dazzling. In fact, I like to take my binoculars out with me even when I'm star observing with my telescope. A look with the binoculars will let me easily find the object of interest, and make it easier to see where to point the telescope.



An Easy Binocular Tripod Adaptor

If you decide to get a larger pair of binoculars, 60mm or bigger, you'll probably need to have some kind of tripod mount for them. Since I'm primarily a telescope user, I'm not interested in a binocular mount that takes more time to set up than my telescope. But here's a very simple mount you can make using your camera tripod.

It's a simple L bracket, available at the hardware store. One with legs about 4" long would be sufficient. One leg is mounted to the tripod, the other to the front of the binoculars. If the tripod is a decent one, this apparatus works well, but kind of kinks the neck if you're trying to look at high elevations.

There are more elaborate solutions for those who really enjoy binocular astronomy. A common solution is the parallelogram mount, like the Orion 5379 Paragon-Plus Binocular Mount and Tripod. This not only holds the binoculars steady, but lets the user easily point and even raise and lower the binoculars with ease. An added feature is that when raising or lowering the binoculars, the binoculars stay pointed at the target. These mounts are great if you're out observing with another person and sharing views, even if the other person is a different size (like a child). If you peruse the web, you can find examples of how to build such a mount.



Binoculars on Tripod

Here you see the 15x70 binoculars mounted to the tripod via the L bracket. The center post of the binoculars usually has a cap that can be removed, revealing a 1/4" screw thread. This is easy to use with the L bracket to make a simple and inexpensive tripod for your huskier set of binoculars.

I usually have the L bracket mounted so that the vertical component is nearest the tripod handle. These brings the binoculars toward me, and the tripod interferes less with observing.



Bincoulars on a mirror mount

15x70 binoculars on mirror mount

If you want the ultimate binocular observing experience, you might consider making or buying a mirror mount like this one.

In operation I mount this apparatus on my camera tripod, adjust the height of the tripod to put the binoculars at a comfortable observing position, and observe in complete comfort (except, perhaps, for the cold).

To move in azimuth, I just rotate the tripod head and roll my rollable observing stool around the tripod. To move in elevation, I just change the tilt of the mirror. With this simple apparatus, I can be looking at the Andromeda galaxy directly overhead with no discomfort.

Covered binocular mirror mount

Here's a picture of the mirror mount with binoculars removed and the mirror covered. Notice the familiar L bracket for mounting the binoculars.

The mirror in this image, which must be a quality first surface mirror to give good results, is covered with a simple cover made from plastic coated foam board. The pieces were cut with a craft knife and glued together to make a tight fitting cover. The cover rests on the pivot verticals, not on the mirror itself.

You can purchase a fine commercial version of this mirror mount at Skywindow. You can also make one as I did from the excellent plans at Binocular Mirror Mount Plans.

At the plans site, the author also lists a source for the mirror, which is in the $60 dollar range. If that link no longer works, you can usually also find suitable 1st surface mirrors at Surplus Shed. If you can't find precisely the size of mirror used by the author of the Mirror Mount Plans, you may have to alter dimensions of your mount accordingly.



Some Personal Comments

Here's a few comments from my personal experience. While I mentioned that moderate priced binoculars can be good performers, I'll give some examples of what you'll find.

My 7x50 binoculars have the brand name Compass. I'm not sure you can find them anymore, and that might have been a store-brand name put on binoculars manufactured by someone else. None-the-less, they've always worked very well, delivering crisp images.

My 16x50's are Bushnell binoculars. They are rugged, very easy to quickly focus, and generally I'm happy with them. The right set of lenses, however, don't give as precise an image as the left. A more expensive pair would not likely have that problem.

The 15x70's are Barska binoculars. That's an inexpensive Chinese import. The first pair were poorly aligned, and the left barrel delivered a pretty poor image. I found a site online that described how to align them, and able to rectify that problem. Still, the left barrel focused poorly.

I sent them back to Barska and received in return a new pair. Both barrels focus crisply. But the new pair also had poor alignment. Having been through it before, I did the alignment process. Now, I can't complain. For little money (less then $100) I have a pair of good performing 70mm binoculars.

But now you can see what a few extra bucks will do for you -- save some headaches.