Using binoculars to project an image of the Sun is an old trick, but it's a good one! However, most older books call for a setup that uses a photographic tripod and is difficult to set up and keep oriented (particularly for elementary school students).
This Instructable describes how to assemble an inexpensive, highly portable, and safe apparatus that can easily be used and built by students.
(I've taken to referring to it as "Sun Trombone," but the kids invariably call it a "Sun Bazooka.")
I first made these as a project for our university's physics-outreach club; we used them to observe the 2012 transit of Venus, but they can be used to check for sunspots any day. And, they'd come in pretty handy for viewing the upcoming solar eclipse on October 23, 2014!
Let's get started!
Step 1: What You'll Need:
This project uses only inexpensive, widely-available tools and materials. The most complicated procedure involved is drilling holes in plastic pipes (this can even be done with a manual drill for added safety).
Here's What You'll Need:
- A pair of binoculars.
(Actually, you'll only need HALF of a pair of binoculars. That means that this project is a great way to re-use an old set of binoculars that has one damaged lens, or which is horrendously out of alignment. There are ALWAYS half-damaged binoculars available at yard sales and junk shops!)
- Some 3/4" plastic pipes
(Originally, I tried making these with 1/2" plastic pipes, but they were just too flimsy. You'll need about four or five feet of 3/4" pipe for this project. Fortunately, in the U.S., plastic pipe segments are usually sold in two lengths: two feet long and ten feet long. If you buy a ten-foot-length of pipe, you'll have enough to make two Sun viewers. If you opt to buy the easier-to-carry two-foot-length segments, you'll need two to finish this project.)
- A 3/4" T-shaped pipe fitting
- (Optional) a cap for 3/4" plastic pipes
- Two L-shaped brackets
(I used the 3" size for this project. The exact dimensions used in later steps will be determined by the particular size of the brackets you use.)
- A clipboard
- Various machine screws, nuts, and washers
(The exact dimensions needed will be determined by the holes in the brackets you use. I ended up using four one-inch-long #10 screws, and two one-half-inch-long #10 screws, with nuts and washers to match. I recommend getting a $1 pack of assorted screws, washers, and nuts -- that should have MORE than enough supplies to get you through this project!)
- A 1/4" bolt and a 1/4" nut
(This is the only component whose size you need to match exactly. We'll be using a 1/4" bolt and nut to attach the binoculars to the bracket. See step ???? for details and some options you might consider.)
Additional Tools And Useful Extras:
- A screwdriver and pliers (for tightening the screws and nuts)
- A drill with bits to match the screws you chose
- A handsaw for cutting PVC pipe (a hacksaw works well)
- (Optional) Some aluminum foil
- A sheet of paper (yellow is fun, but other colors work just as well)
Step 2: Make Your Frame
The exact dimensions of the frame aren't important; you can experiment with different lengths of pipe to achieve the right fit for your users. (Adult-sized Sun Viewers can become unwieldly for elementary-school students, so it's useful to tailor your Sun Viewer to your intended users.)
Cut The Pipe:
- For an adult-sized Sun Viewer, you might try cutting the pipe into the following three lengths:
- One 36" piece
- One 18" piece
- One 6" piece
- (Note that you can make two adult-sized Sun Viewers from a ten-foot length of pipe.)
- For a kid-sized Sun Viewer, try cutting the pipe into the following three lengths:
- One 24" piece
- One 18" piece
- One 6" piece
- (If you purchased two 24" pipe segments, you'll only need to make one cut for this size Sun Viewer.)
Once you've got your three pipe pieces, use the T-shaped fitting to attach them into something that resembles a policeman's night stick. (Have a look at the photo above; it's what ten-year-olds invariably see in this shape.)
Step 3: Attach the Brackets
Attach the two metal brackets to the ends of your pipe frame. (The exact spacing, hole size, and screw size will be determined by the brackets you use.)
Step 4: Attach Your Binoculars to the Bracket
We'll be attaching the binoculars to the bracket on the shorter pipe, as shown in the pictures.
This is the only step that requires a specific-sized bolt.
Every pair of "grown-up" binoculars has a standard-sized, threaded attachment point in the middle. (To expose it, you might need to pry off, unscrew, or otherwise remove some kind of cover.)
Binoculars, cameras, tripods, and all manner of optical equipment use a 1/4"-20 thread. (This means that it's 1/4" wide, and there are 20 screw threads per inch.) This is also called ' 1/4" coarse ' in hardware stores.
To attach your binoculars, you'll need a bolt of this size.
You could simply use a 1/4" screw or bolt and tighten it down against the bracket. However, for a "no tools required" version, follow the steps in the photos. (That way, you won't need to carry around any tools in order to make adjustments in the field.)
Step 5: Attach the Clipboard
Using your bracket as a guide, drill two holes in the clipboard. Then, secure it to the bracket with two screws. Then, add a sheet of paper to the clipboard.
Step 6: Cover Up One Binocular Lens
That is, turn your binoculars into a monocular.
(Lens caps are traditional, but aluminum foil works exactly as well.)
You're finished building your Sun Viewer! For some tips on using it, see the next steps.
The safety advantage of this Sun Viewer is that, unlike a pair of binoculars attached to a tripod, it encourages users to face AWAY from the Sun (reducing the risk of fried eyeballs).
A practical advantage is that it's both very stable, and very easy to adjust when the user needs to follow the Sun's apparent movement across the sky.
How To View The Sun Safely:
- Stand facing AWAY from the Sun.
- Hold the Sun Viewer with the binoculars resting on your shoulder and the clipboard in front of you.
- (This part takes a bit of practice.) Wiggle the Sun Viewer around until you can see the binoculars' shadow on the paper. With a little bit of adjustment, you'll notice a bright circle appearing in (or near) the binoculars' shadow. That's an image of the Sun!
- Carefully alter the position of the Sun Viewer and your head until you can see the shadow of your head on the paper. Then, try to get the image of the Sun to appear INSIDE the shadow of your head. (Using your head's shadow not only provides you with a higher-contrast image of the Sun, but it makes your shadow look like a cyclops.)
- It'll likely be a bit blurry, so you'll need to focus the binoculars. Do this the same way you normally would, by adjusting the binoculars' focus knob. (This is where it'll REALLY feel like you're playing a Sun Trombone.)
- Once the disk has a sharp, well-defined edge, look in the interior of the solar image for sunspots.
- For Extra Learning, check out a current image of the Sun from the Solar Dynamics Observatory satellite. Can you find the same sunspots? What does their position tell you about your image of the Sun -- is it inverted left-to-right, or up-to-down?
Another handy feature of this Sun Viewer is that it allows other students to take photographs of the solar image with regular cameras. (No filters required!)