Binocular Basics

Binoculars are a great inexpensive way to look deeper into the cosmos.

If you are thinking of getting a telescope start with a pair of binoculars first.

1. Why Use Binoculars?

The right pair of binoculars can provide a low-cost entry into astronomy and let you see countless objects in the sky. One of my most enjoyable experiences was taking a pair of binoculars in a dark sky and sweeping across the milky way.

Finding objects in the sky can be difficult and is more so at high magnifications. Binoculars with their low magnification and wide field of views make it easy for a beginner to find objects in the night sky.

A good pair of astronomy-worthy binoculars will be between $40-$120. Large pairs of binoculars can be a joy to use as well and cost hundreds but are not recommended for beginners. Do not size up to a 20 x 80 unless you are experienced with a 10 x 50 and understand how to handle the additional weight and magnification.

My preferred budget option is the Celestron Upclose G2 10x50 and they can come with a variety of accessories. My personal favorite binocular is one that will last decades if taken care of, the Nikon Aculon A211 10x50. If you can afford to get the Aculon A211 it is very much worth it.

2. Understanding Aperture and Magnification

Binoculars are typically described by two numbers (and are often in their names), their magnification, and the aperture (sometimes referred to as the objective lens) or the size of the lenses at the front.

The most recommended type of binoculars for astronomy is a 10 x 50. The first number is the amount of magnification they provide. The second is the size of the lens used to gather light. 10 x 50’s are a good balance between weight, magnification, and aperture. If you have particularly shaky hands and do not plan to use binoculars with a tripod an 7 x 50 or an 8 x 40 may be a better option. If you already own a pair of binoculars they should have their magnification and objective lens size listed on the side or in the middle of the eyepieces.

Our hands shake slightly even when we are still and when looking at a magnified image, those hand-induced vibrations are magnified as well.

A pair of 7 x 50 binoculars

3. Focusing Binoculars

Binoculars have a primary focusing wheel in the middle. Your binoculars may also have a diopter adjustment that allows for focus differences between your eyes to be accounted for. The diopter adjustment is typically on the right eyepiece.

First with your right eye closed use the primary focus and rotate the focus until the image is sharp. Once the primary focus is set open your right eye, close your left eye, and rotate the diopter adjustment until the image is sharp. Now the image shown in the binoculars should be sharp in both eyes. If you do not have a sharp image in both eyepieces set the diopter adjustment to neutral and start over. There usually is a zero mark for the neutral position.

Finally, adjust the distance between the eyepieces by bending the binocular on its main hinge. Adjust until there are no vignetted edges. The view should be very slightly elliptical being slightly wider than tall. For objects that are close by you may have trouble merging the two images.

4. The Moon and Planets

Watching the moon with a pair of binoculars is always enjoyable. You can see the craters on the moon and during the first or third quarter moon (when the moon is half full) you can start to see the mountains on the terminator (the day-night transition).

Jupiter’s Galilean moons Ganymede, Callisto, Europa, and Io can be seen but require a steady hand or mounting the binoculars on a tripod. Saturn’s ring start to be visible with the planet no longer looking like a point but an oddly shaped oval.

The phases of Venus also begin to become visible with Venus appearing as a small moon-shaped object with its shape dependent on its location in its orbit.

Binoculars are also perfect for eclipses. Watching a lunar eclipse can be safely done with a regular pair of binoculars. A solar eclipse requires appropriate filters. Never point a pair of binoculars toward the sun without the use of appropriate filters. If you are unsure if what you are doing is safe it is always safer to stop and check or ask for help.

5. Binocular Deep Sky Objects

The Andromeda Galaxy through 10 x 50 Binoculars from suburban skies

Binoculars can let you see many deep sky objects even in light-polluted skies. A telescope will show you more but it is hard to beat the zero set-up time of grabbing a pair of binoculars. From a truly dark sky, the entire Messier catalog is visible with a pair of 10 x 50s.

If the Andromeda galaxy is up in the sky (August to March) it should be the first deep sky object you take a look at with binoculars. Its faint fuzzy glow can be seen in very light-polluted skies with the fainter extensions of the galaxy visible in dark skies. Being over 2 million light years away it is always exciting to see.

Large open clusters such as the Pleiades, Hyades, Beehive Cluster, Brocchi’s Cluster, Ptolemy’s Cluster, and Perseid Double Cluster are all easy star clusters to find and observe with binoculars.

The Orion Nebula and possibly the Lagoon Nebula are the only easily seen nebulae in binoculars from light-polluted skies.

The brighter globular clusters such as M2, M3, M 5, M 13, and M 92 are all visible from suburban skies with many more able to be viewed in dark skies.

6. Binocular Tips!

  1. Use a tripod

    Binoculars are considered as low magnification in astronomy but even at 10x, the view can be unsteady. Jupiter’s moons are impossible to see handheld but easy with a tripod. Using a tripod and binocular adapter can make viewing the sky much more comfortable. If you already have a tripod at home feel free to use it.

    Most binoculars have a cap covering the mounting screw on the objective side of the focus. Some caps unscrew while others simply pop off.

    My favorite on-the-go tripod to use with binoculars is the Small Rig 71” Tripod. I like to use adapters that can quickly be removed such as the Staoptics Binocular Tripod Adapter. A more heavy-duty adapter should be used for binoculars larger than 10 x 50s.

  2. Relax with a lawn chair

    Bending your neck to look up is not comfortable and sitting down on a lawn chair can allow you to comfortably gaze toward the zenith (the highest part of the sky).

  3. Use a filter

    In a dark sky using a UHC (Ultra High Contrast) or OIII (Oxygen 3 filter) can let you look at large faint objects such as the Veil nebula, or bring out more detail in smaller nebulae such as the Dumbell (M 27), Swan / Omega Nebula (M 17), or Lagoon Nebula (M 8). Since most binoculars do not have a way to directly mount these filters this is only recommended for experienced observers.

Jupiter and the Galilean Moons through 10 x 50 binoculars