This is an easy and cheap telescope that can be made out of a few commonly available items and some cheap lenses. There are a lot of variables that you can tweak to make this design work with what you have on hand, it will just take some patience, measurements, and ingenuity - something an Instructable user has in spades!
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Materials and Tools Required
You'll need the following, or some variation:
- Lenses. I bought these cheap lenses from Amazon, and paired them with some of the plano-convex lenses leftover from this kit. If the kit is available from that website (it comes and goes, I've found), purchase that and you are set!
- Two toilet paper tubes that fit inside of each other. I find that a TP tube and a paper towel tube are a great combination - the paper towel tubes are typically just a bit larger.
- Part of a 2" mailer tube - easy to find at your local post office, just ensure the inside diameter is 2"
- Masking tape and scotch tape
- A film canister or small diameter tube that fits the eyepiece
- Craft Foam
- A silicon-based adhesive - E6000 works fine, regular silicone also is good or something like Amazing Goop. In a pinch, I'm sure hot glue will hold.
- Optional: I designed and 3D printed a cowling to secure the lens to the front. The file is included, you'll have to either design or modify depending on the lens that you use. If using the 3D printed piece, silicon adhesive is recommended to secure the lens in the cowling. If not, simply tape the lens to the front of the mailer tube or find another creative way to attach it.
Step 2: Secure the Lens in Holder
To make the main assembly of the telescope, put a thin bead of silicon where the lens will seat (don't use too much!) and push the lens into the cowling. This will need to cure for a few hours before doing too much with it, so do this step first then grab lunch, leave it overnight, or whatever. Once cured, the lens won't be going anywhere. Stick the cowling into the 2" mailer tube and you are done with this part. For my lens, the focal length was roughly 4". This means that the main tube for the body of the telescope is only 3". I cut the tube using my band saw, you can use a box knife, jigsaw, or even a hacksaw to cut the tube. Try to get an even cut or use the flat edge on the the side that the cowling fits into.
Step 3: Make the Focuser Holder
Now, it's time to take your larger TP tube or paper towel roll tube and insert it into the mailer tube. I use a piece of craft foam and some tape to shim it so that it fits snugly. As long as it's just about flush with the back of the mailer tube when inserted, you have the right length. In this example, I just cut the tube in half to be about 2" long. If it's too long, you may not be able to get the eyepiece pushed in far enough to focus properly.
Step 4: Make the Focuser
Take your lens and a film canister. Cut the closed end off the film canister - box knife works great, as does a bandsaw, PVC cutter, etc. Be careful not to cut yourself! Set the lens on top of the film canister and apply some scotch or masking tape around the edge of the lens so it stays on the film canister. Don't put tape over the surface of the lens or it'll be cloudy - just around the outside. Now, take a strip of craft foam about 1.5" wide by 12" long and wrap it around the film canister, taping the end in place. You'll have to play with this part to get the right amount - add more tape or cut off some of the craft foam as necessary.
Once done, it should fit snugly inside the smaller TP tube. Leave that tube the full length. If the tube fits too loose inside of the telescope, simply add a few layers of masking tape to make it a better fit. I like to add a little tab of masking tape at the end in case the eyepiece gets shoved all the way inside the tube. Simply take a 6" piece of tape and fold it over so you have a 3" piece with no sticky stuff exposed. Tape that down to the end of the focuser and you're done.
Step 5: Use and Telescope Safety!
As with any instrument that provides magnification, you should NEVER EVER look at the sun with it. The light from the sun when magnified in any capacity will ruin your eyes permanently, and could blind you. Always, always, always ensure that you're not looking in the vicinity of the sun when using any sort of binoculars or telescope during the day. With this little telescope, the moon will look cool and you should get about 3-4x magnification. You may even be able to see the moons of Jupiter on a clear night. To use, simply point in the direction of what you want to see, and slide the eyepiece forward and backward until the object appears clear. Enjoy!