How to Choose Binoculars
[This is part one of until-I-get-tired in a series on buying and using binoculars.]
I’ve never really liked using binoculars for looking at the night sky. They’re OK, but they make my arms tired when I try to look at something for any length of time, they have low magnification, and are about as expensive as a small telescope.
Of course, that doesn’t keep me from owning five pair.
One thing they can’t be beat for however, is portability. Lately, I’ve been taking walks around a nearby lake at night and I’ve taken a pair along. I’ll sit on a park bench and look at the crescent moon, Saturn, and Venus almost every night:
Image Credit: Lil ole me, ummm, and Stellarium
A couple of nights ago I was out and I thought I’d do a few posts on what to look for in a pair of binoculars, how much to spend and define some of the terms specific to binoculars.
To begin, I don’t think you should get a pair of binoculars solely for looking at the night sky. As I said, I much prefer small telescopes for that, if for no other reason than they have a mount. Instead, buy binoculars that you can also use to take to sporting events, concerts or bird watching.
Binoculars are classified by two characteristics: magnification and diameter of the objectives (aperture). So, a pair of 7×50 binoculars have objective lenses (the lenses out front) that are 50mm in diameter and provide a magnification of 7 power, 10×50’s have 50mm lenses and give 10 power, and so on.
I find that 10 power is about the maximum you can use and keep your hands steady enough to see anything, 7 power is actually better. I have a pair of Nikon 10×50’s that I can barely keep steady, that magnification is really too high for any kind of long term viewing without a tripod.
I took those to a Broncos game once, and because of the vibrations in the stadium during the game, I couldn’t even use them. I take my 7×35’s to all ballgames now.
For astronomy use, I recommend 7×50’s. The objectives are big enough to give a bright image and the magnification is enough to show you the craters on the moon, the rings of Saturn, and the bands of Jupiter are sometimes visible if the sky is clear and dark (which it almost never is where I live, but you know how I feel about that).
7×50’s are also versatile enough to take to concerts and use for other things. I really don’t recommend 10 power binoculars for much unless you can mount them on a tripod.
There are also two main styles of binoculars, porro-prism and roof-prism. Each of these use a different prism that aligns and rotates the image for your eye. Roof prism binoculars are generally straight tubes where the light comes in the objective and out the eyepiece with no bends, while the porro-prism binoculars have a bend in them.
Porro-Prism Binoculars
Roof-Prism Binoculars
There really is no advantage to one style over the other, roof-prism binoculars are more compact, so I like those a little more. Any decent pair of binoculars will yield good views regardless of the style but, like anything, you get what you pay for.
Which brings me to price. How much should you expect to pay for a decent pair of binoculars? First, I’m going to recommend that you stay away from Bushnell and similar brands. They usually cost about $69.95 or so; I have yet to see a pair of binoculars in that price range that didn’t make my eyes hurt. If you want a decent pair of binoculars that will last a lifetime and that give you comfortable, in-focus viewing, expect to pay no less than around $179.00.
Next time, I’ll post on what you can expect to see with them and some qualities that are important, like exit pupil.
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