Build a 3D Printed Collapsing Telescope

In this Instructable I'll be showing you how to build your own collapsing telescope for only $20! We will building a Keplerian refracting telescope, which uses two lenses, an objective lens and an eyepiece lens. The objective lens will have a focal length of 500mm and the eyepiece lens will have a focal length of 50mm, so our telescope will make things appear 10x bigger. Feel free to experiment with different focal length lenses to make higher power telescopes, as long as the diameter of the objective lens is 75mm and the diameter of the eyepiece lens is 38mm they will fit into the telescope body.

3D Printed Parts

1x body 1-4.stl

1x small lens holder.stl

1x big lens holder.stl

Other Parts

Super Glue

1x Double convex lens with 75mm diameter and 500mm focal length (you can get one here)

1x Double convex lens with 38mm diameter and 50mm focal length (you can get one here)

You can find the project files on my Printables. I designed this telescope in Tinkercad, and this project has been a great learning experience. It took me a while to figure out the collapsing mechanism, and I went through a couple iterations before landing on the final you see now. The current design uses a small lip around the top of the cylinders and a stopper at the bottom to make the collapsing mechanism.

Start with the bigger lens. You will see a lip on the inside of the lens holder that is closer to one side of the holder than the other. Apply glue to the side of the lip that is closer to the top of the holder and set the lens on top of the glue. It shouldn't matter which side of the lens you put facing up, however if you notice that one side of lens is more curved, place this side facing down. Do the same process for the smaller lens, with the more curved side also pointing down. Let the glue dry.

While you let the glue on the lens pieces dry, lets set up the rest of the telescope! First, grab the two smallest cylinders. If you look at the two cylinders, you'll see that both have a slightly raised lip on one side. Flip the cylinders so that the lip is facing up on both, then take the smaller one and place it into the bigger one with the lip still facing up. You may need to file down the bottom of the cylinder for it to slide in, but it should be able to just barely fit through the hole on the bottom of the bigger one. Once it's in, you can pull it down and the lip should stop it from falling out. Now, take the next biggest cylinder and place the first two inside it with the lips of all three facing up. Once again, you may need to file the second cylinder down before it slide in. Finally take the last cylinder and place the other three inside it.

Once the glue dries on the lens holders, just slide them onto the end of the telescope. The larger lens holder will fit snugly onto its end while the eyepiece will fit more loosely. Once you put them on, look through the telescope at something far away. You might notice that the object you are looking at is fuzzy or inverted. This is because of small imperfections in the lenses that cause the focal length to be slightly off. To fix this, simply adjust the small lens holder by moving it up and down until the image in the eyepiece focuses. Congratulations! Your telescope is now all ready for exploring the wonders of space.