The Basics Of Binocular Astronomy

The Basics Of Binocular Astronomy

Guess What.  You Don't Always Need a Telescope.  Here are Some Amazing Things you Can See with Binoculars in the Night Sky. 

Andromeda galaxy through binoculars.png


It's a simple fact.  Setting up a telescope for a night of viewing the skies takes some time and effort.  This assumes you own a scope and have the place to store it.  What many of us forget is that a pair of binoculars can give us a chance to take a quick look or spend an evening observing the moon, planets and even some deep-space objects such as the Andromeda galaxy, nebulae and significant events such as lunar eclipses and comets.  Chances are, you have a pair of binoculars and you may surprised by what you can see. 

Image above is a simulation of the Andromeda Galaxy through binoculars by Roberto Mura.


How To Choose Binoculars For Astronomy

To begin with, you need to understand a bit about binoculars as it relates to astronomy.  On most binoculars you will see some numbers.  Look for the combination with an "x" in the middle.  For example you may see "8x40."   This is telling you two things.  The first number is the magnification.  A "8" indicates that objects will appear 8 times closer.  The second number is telling you the size of the front lens in millimeters.  In this case, 40 millimeters indicates the diameter of the lens at the wide end of the binoculars.  This is often referred to as the "aperture."  That's important because the wider the aperture the better the light gathering ability.   Light gathering is critical for astronomy given that we're typically doing this in the dark.  However, there is a downside.  The wider the aperture the heavier the binoculars.  That can get wearisome without a tripod. 


The magnification is also important.  8x sounds good but aren't we all tempted to say I want 10 or 15x.  Here again, that could work assuming you have a tripod for your binoculars.  The advantage of binoculars with a modest magnification is related to field of view.  Most astronomical viewing with binoculars is hand-held.  If you have significant magnification you're going to have a smaller field of view.  This "field of view" is sometimes expressed as a number on your binoculars measured in degrees.  10° gives you a wide field of view while 2° would be very narrow.  Kind of like looking through a straw.  This can make it tough to find the objects you're looking for especially if you have a large aperture on a heavy set of binoculars. The other problem with too much magnification is that the higher the magnification the more your hand tremor is magnified too. A shaky image will make looking at anything a chore.


If you want to go for it, the Olympus 8x40 or 10x50 might be right for you. You can read a review on them here.

The Advantages Of Binoculars

There are some interesting advantages with binoculars.  For one, you're using both eyes.  This helps with light gathering ability.  Binoculars also show you objects "right-side-up."  Some telescopes actually give us an image that is upside down.  A fact that we soon recognize those first few times we're trying to track an object manually through a telescope.  A right-side-up view makes it a lot easier to understand the geography of the moon especially if we're using a lunar map as reference on a computer a photograph or the new app from NASA

What Can You See

But it's not just about the moon and the planets.  From autumn through spring the Andromeda Galaxy will appear as a dimly glowing little oval cloud.  In Winter, scan the Hyades and Pleiades star clusters.  There's also the Great Orion Nebula in Orion's sword.  All are discernible through binoculars if you know where to look.  It's not just about the moon.  It's estimated there are 400 deep-space objects that can be seen with binoculars. 

Orion Nebula - Hubble 2006 mosaic 18000.jpg

Orion Nebula by NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team

With so much to see combined with the grab and go ease that binoculars provide. Why not dust off your pair or purchase a nice new pair and go have a look at the night sky.

Here is a good pair of inexpensive binoculars for astronomy to get started.

Related Posts: Astronomy Equipment

Back to the Learn Astronomy blog

Don’t forget to sign-up for the newsletter below to receive updates when new content is released. Your email address will not be shared.

Or leave a comment I’d love to hear what you think about the article.

If you enjoyed this, sign up for the newsletter

 Privacy policy and cookies | Disclaimer | Contact Us | Credits | Resources | Site Map © 2012-2014