Binocular Frame for Backyard Astronomy

The night sky is alluring, and holds its own special beauty for those who take the time to stand out in the backyard, look upward, and contemplate this vast, magnificent Cosmos we are a part of.

You can easily enjoy the night sky with your naked eye simply by looking at the patterns of the constellations, or watching a moonrise. Telescopes provide an unprecedented ability to see the Universe up close, if you are fortunate enough to own one or have a friend who is willing to give you a tour of sky through theirs.

But telescopes require some monetary resource to acquire, a bit of a learning curve to learn how to point them, and some tinkering to use effectively. All of these points may be challenging for an aspiring stargazer to overcome. What are you to do if you don't have the money to invest in a telescope, or the time to learn how to use one?

Fortunately, there is a middle ground that makes the sky more readily accessible to everyone: binoculars. Any pair of modern binoculars is as good as, if not better than, the very first telescopes used for astronomy by Galileo and his contemporaries, and will show you awe inspiring views of the Universe.

This Instructable will show you how to build a simple stabilizing frame that can help you point your binoculars easily to see the sights in the night sky with a little bit of wood from your scrap bin. So grab those $10 birding binoculars living under the seat of your car, and let's look at the night sky!

This Instructable is common design that is used in the amateur astronomy community. The earliest design of it I can find can be seen in this article by Alan Macrobert, which appeared in Sky & Telescope in 2009.

There are no fixed dimensions for these binocular frames, but most are about 5 foot long (this makes the physics behind how they work possible -- see Step 12), and wide enough to put your head through with the rails resting on your shoulders. I sketched out the basic pieces, and note the sizes I settled on in the materials list below:

• Wood Rails (2) : 1" x 2" x 60"
• Rear Weight Board (1) : 2" x 7" x 9"
• Mounting Board (1) : 2" x 7" x 9"
• Binocular Strut Board (1) : 1" x 2.75" x 8"
• Front Handle Dowel (1) : 1" x 9"
• Short Bungie Cord (1) or Elastic Hair Ties (~6)
• Cup Hooks (2)
• Pipe Foam (2) : 16" length
• Pair of Binoculars

The overall width between the frame rails is 9".

You can certainly buy wood stock in the common widths noted in the materials, and then jump immediately to the next step. However, if your shop is like mine, you have a bin with all your wood scraps in it because all wood is good for something!

I keep mine in the garage in three wardrobe boxes left over from when we moved -- the wardrobe boxes are tall and sturdy, and perfect for holding wood in a contained space!

When I can, I like to use wood from my bin first, so I don't have to start with a new pristine piece. I start with the smallest ones I can find and use, so I minimize the waste of wood, and also so I have longer pieces still around when I need them!

For the project shown here I made pieces that you could use raw stock for. These included:

• Ripping the two 1x2 rails from a scrap 2x2 using my table saw
• I cut the Binocular Strut from an old broken 1x4 (with only one broken corner still visible)
• I cut the Rear Board and Platform Board from a 2x10 end left over from resurfacing our deck.

Most of the pieces are straight forward to cut to length, but the binocular strut board requires a bit of attention. It is the piece that your binoculars rest up against, so it has to be cut to a width that fits between the lenses of your binoculars!

For the binoculars I'm using (7x35 birding binoculars), when the binoculars are opened to their widest they are about 3-5/8" apart and when they are closed to their smallest they are about 2-3/4". In order for the frame to be used by anyone with these binoculars, the strut board cannot be any larger than the smallest separation between the lenses.

I ripped the piece I used for my binocular strut from a normal 1x4 width down to 2-3/4" wide, so it always fits between the binocular lenses.

The entire assembly is put together with drywall or wood screws. I pre-drill all the holes for the screws -- it is a little more time to do that, but it make splitting boards far less likely!

The beginning of the assembly is to attach the Rear Weight Board (2x7x9 inch board) to the rails using two screws on each side.

The second part of the assembly is to attach the front handle (1x9 inch dowel) to the two rails using one screw on each side.

The Binocular Strut is screwed into the center of the Mounting Board using two screws, with about 4" of the strut sticking up above the edge.

The mounting board provides a small shelf the binoculars rest on, and the strut board sits flush against the binoculars between the lenses, holding the binoculars in place.

The two cuphooks will be part of the attachment system -- screw them into the lower corners on the opposite side of the mounting board from the strut, as shown in the third image above.

At this point the frame is a reasonably rigid rectangle, and you can put it over your head to "take it for a spin." This is necessary to decide where to put the mounting board for the binoculars.

Put the frame over your shoulders, with most of the length behind you. Hold the frame by the front rail, with your arm slightly bent as shown in the image above. Wherever your face is located is roughly where the mounting board will be attached. Carefully make a mark on the rail just in front of your nose.

On my binocular frame, this point is 10.75 inches back from the front of the frame.

The Binocular Mounting Board is attached to the frame through the rails, but is allowed to rotate slightly so you can adjust the binoculars to a comfortable observing position.

First, drill one hole through each rail that is wide enough to let your mounting screws slide freely through them. I used 1-5/8" drywall screws in my assembly, and just hold a drill bit up behind the screw until I find one that I can't see the threads behind. After you drill the hole, make sure the screw goes through it without needing to be forced.

In order to provide a little bit of friction to hold the mounting board in place (it should only move if you push hard on it) I put two toothed lock washers on the drywall screw -- one on the outside of the rail (under the screw head) and one between the rail and the mounting board.

Make sure the binocular strut is facing the front handle!

Drill the mounting screw into the mounting board -- the screw should not be free in the mounting board. Since the threads are allowed to grip the mounting board but not the rail, the two screws on either side act like a kind of axle that the board can pivot on. The lock washers provide friction so it doens't tip back and forth easily. If it does tip easily, tighten the screws down so it does not.

Many people use a short bungie cord to mount the binoculars to the frame. I've never liked this because bungies pack quite a wallop if they were ever to come loose. One solution would be to use velcro straps, but I like to make my own elastic cord using hair ties.

To link them together, lay two ties across one another, fold one over and pull it through itself, then pull it tight. A link of 6 hair ties is enough to hold my binoculars.

To mount the binoculars, hook one end of the hair-tie chain over a cup hook. Holding the binoculars against the strut board, pull the hair ties between the eyepieces, around the front of the strut board, back between the eyepieces, and down to the opposite cup hook.

Your binoculars should be held firmly against the strut board!

The wooden rails will dig into your shoulders, especially during the summer when you might not be wearing a heavy coat. To alleviate this, I put small lengths of pipe foam over them.

The particular foam I used in this project came on a white board, so it was ideal for putting over a square board (lesson: recycle everything! You never know when it might be useful in a project!)

To use the frame, place it over your shoulders and turn to face the direction of the object you would like to observe.

Because the frame is LONG, observe standing away from others, and do not turn suddenly! You may accidentally hit someone with the back end (if you have extra pipe foam, putting it around the rear weight board is an excellent precautionary measure).

Grabbing the front handle, pivot the frame up or down so it is pointing in the general direction of your target, and adjust the tilt of the mounting board back and forth a bit so it is comfortable for you to put your eyes up against the eyepieces.

Adjust the focus with one hand while holding the front rail with your other hand.

The frame should be reasonably steady; I sometimes observe with my hand on the front rail, and sometimes with both hands holding the side rails just in front of the mounting board.

There are many good books dedicated to doing astronomy with binoculars. Two of my favorites are:

• Binocular Highlights, by Gary Seronik
• Stargazing with Binoculars, by Scagell & Frydman

If you don't have books though, you can still get started with a few targets in mind, listed below. In my Planisphere Instructable, I've included a star chart with things to see in binoculars so you can hunt them down yourself.

THE MOON. Probably the coolest thing to look at with your binoculars for the first time is the Moon. The image above was taken with my phone through binoculars. If you look at the Moon with your naked eye, you can only see the patterns of light and dark, but binoculars will show you much more detail!

ANDROMEDA GALAXY (M31). Under dark skies, the Andromeda Galaxy can be seen with the naked eye, which makes it easier to point your binoculars at. Through the binoculars it will look like an elongated fuzzy cloud with a slightly brighter center. The light you are seeing when you look travelled through space for almost two-and-a-half million years!

Pleiades (Seven Sisters). The familiar constellation in the logo of Subaru cars is visible to the naked eye as a small cluster of stars, but through binoculars looks like a handful of sparkling gems dropped on a black piece of cloth.

Orion Nebula. Orion is most easily visible in the northern hemisphere's winter, not far from the Pleiades. The middle "star" in Orion's sword is not a star, but a vast cloud where new stars are being born, a "stellar nursery." Visible to the naked eye, a pair of binoculars makes this appear as a fuzzy swirled cloud.

Lagoon Nebula. During the Summer in the northern hemisphere, Sagittarius is visible near the southern horizon. Just over the "teapot" shape of the constellation is a small fuzzy patch that looks like steam coming out of the teapot. This is another stellar nursery called the Lagoon Nebula, and looks bright and fuzzy in binoculars.

Double Cluster. Just off of the left side of the "W" shape of the constellation Cassiopeia is a pair of side-by-side star clusters where new stars have recently been born and will soon wander away into the galaxy. These kinds of clusters are called "open clusters."

Let's talk about why this works. This Instructable was written during the 2020 Pandemic, when many of us are at home, and are helping our children work their way through classes. This binocular frame is an engineering project, but the principle by which it works is a perfect example of how science (physics in this case) is used in everyday life. I wanted to visit this briefly, in the hopes that it might illuminate one of the more obtuse topics often covered in introductory physics, called "rotation and moment of inertia."

"Moment of Inertia" is a bit of physics jargon that tells us how hard is it to make something rotate (or equivalently how hard it is to stop something from rotating). It depends on both the size of the object and on the mass of an object.

In the figure above, I've sketched the basic idea of how changing the moment of inertia makes it easier or harder to rotate an object. Three classic objects to imagine are a marching parade twirling baton, a weight-lifting barbell, and the long balancing stick used by a tight-rope walker. Each of them is easier or harder to rotate than the other because of its mass or its size. Bigger objects are harder to rotate, and heavier objects are harder to rotate.

For this instructable the "object" is our binocular frame, which has more mass than your binoculars (mostly concentrated in the weight board at the back) and is much longer than your binoculars. The result is a stabilizing effect -- the frame is hard to rotate (it has a "large moment of inertia"), so when slight motions in your pointing would normally make the viewing jump around, the frame tries to "stop the binocular frame from rotating." Just by themselves, when you are holding them up to your eyes, the binoculars are very small, and we say "they have a small moment of inertia." This means they are easy to rotate, which is why it is difficult to hold them steady when you are looking through them.

When we attach the binoculars to the frame, they act as one object -- we effectively made the binoculars bigger, which means the moment of inertia is larger, which makes them harder to rotate! When you look through them now, they don't move as quickly or as much, so the image is more stable.

It is impractical to make the frame even longer for more stability, but adding weight to the back end of the frame will also increase the moment of inertia and make the frame harder to rotate.

With homebuilt astronomy equipment, there is a certain degree of tinkering and adjustment to be done. Things that make sense in the design sketch or at the workbench need to be tweaked a bit once you go out at night and use the equipment. For that reason, I tend to wait on finishing until I've used my new creation a couple of times.

Once I've taken the binocular frame out for a spin and am comfortable with the weight and the positioning of the binoculars themselves, I'll give the frame a nice finish. Wood can be sanded and varnished with several coats of spar urethane. But since I've used many different woods to create this frame, I'm planning on painting it. Because it sticks out behind me, I don't want people walking into it and hurting themselves in the dark, so I'll paint the part of the frame that goes behind my shoulders WHITE to make it more visible in the dark. The part of the frame that is in front of my shoulders I will paint a dark color, like NAVY BLUE, to reduce the distraction my eye will see when I'm trying to look at something in the night sky.

There are two improvements that can be made almost immediately to make the frame more versatile, depending on your budget and woodworking skills.

The first is the binocular attachment. Most binoculars have a threaded attachment under the pivot that lets them attach to a tripod. I would like to carve a vertical slot in the binocular mount board, and attach the binoculars to their tripod mount through the slot with a 1/4-20 threaded screw attached to a hand knob. This will remove the need for the binding cord, and allow the binoculars to be easily repositioned securely for whoever is using the frame and for whatever is most comfortable for them to observe.

The second is a sight to help point the frame and more easily find targets. A useful addition would be a red-dot sight, like used for airsoft and bb-guns, which could be mounted directly on the top of the strut board, to show me where the binoculars are pointing.

I hope you build your own binocular frame and spend some time using it to look at the Cosmos from your backyard. If you do, please post a photo in the comment below! Happy stargazing!