Left: Use a boxcutter to scrape the inside of the pipe and enlarge its inner diameter. They can be bought from a variety of sources. For more information, visit their main page or their telescope-building page. We used a boxcutter to scrape along the inside of the entry to the pipe to create a smooth area large enough to just slip the objective lens into. However, for students who have not yet observed the heavens, a 9x Galilean telescope should make an exciting starter scope. Focal length is the distance from the lens to the point where the telescope is in focus, and is measured in millimeters. Drill small holes around the outside of the inner tube, where the lens will be. Cut two pieces from the inner tube, approximately 1 to 1.5 inches (2.5 to 4 centimeters), to create spacers to hold the objective lens. Divide that length by two and then add another inch. We purchased flexible PVC pipe with an interior diameter of 1.5 inches, which was small enough to slide into the larger pipe. You should keep in mind, too, that a Galilean telescope has a small field of view, which means, for instance, that you won't be able to study the entire face of the moon at once. Add glue through the holes, and turn the lens to spread it around. New York, Our lenses were 47 and 49 mm, or 1.8 and 1.9 inches, while the only PVC pipe we could locate came with an interior diameter of either 1.5 or 2 inches. Future US, Inc. 11 West 42nd Street, 15th Floor, A do-it-yourself Galilean telescope makes an excellent and inexpensive starter telescope — or science fair project. Right: The cardboard tube we used for one of the lenses was too small, so we added a piece of cardboard shaped like a watch with no face, which worked great. Editor's note: Contributor Nola Taylor Redd enlisted her children — Dawn (12), Michael (10), Jimmy (8), and Candy (6) — for this project. Most of the materials you'll need can be found at office supply stores or hardware stores. And if you have a news tip, correction or comment, let us know at: community@space.com. For example, using a 50-millimeter lens on a telescope with a focal length of 450 mm would get you a power of 9x. An electrician's punch will also serve. Set aside. Details of Jupiter, such as its famous Great Red Spot, will not be visible at 9x, and Saturn's rings should be visible as a disk, but not with great detail. The material and tools for this project are: Note: Our photos show flexible piping, which we started out with, but upon completion we preferred a straight pipe. This project was inspired by the Galileo Project, hosted by Rice University in Texas. A diagram of how a Galilean telescope works. Please refresh the page and try again. We opted for a magnification of 20x, which resulted in a longer telescope than we could find from an office supply store. Gluing the spacers in place allow the eyepiece to be adjusted as necessary. The most important determination you will want to make is how great your magnification. The Galileo Project website, which inspired the creation of our large telescope, lists plans for building a sufficient base. Determine the how far into the tube the lens and spacers need to sit, then drill small holes on the sides of that region. However, we went with a smaller surplus company that ships, in part because they are relatively close to us (we took the time to get feedback from the owner on our purchasing decisions). Their stock is less expensive, but also somewhat touch-and-go. We found success with a toilet paper tube, though a paper towel tube should also be effective. Right: Insert the cardboard eyepiece into the pipe. Slide the lens and cap into the outer tube. The telescope can be focused by sliding the cardboard tube as necessary. Cut the closed end of the outer tube. Use the drill to make an eyehole in the center of the cap, using light pressure. The removable cap on the end of the outer tube will become the eyehole. Place the flat end of the eyepiece lens against the removable cap. Slide the first spacer in; insert glue through the relevant hole, moving it slightly to spread it around. It is important to keep the cut as smooth as possible. The convex side faces outward. 1. Slide the inner tube into the outer tube. Edmund Optics has a variety of high-quality sizes and focal lengths that can be matched to achieve your magnification goal. Once the correct focusing distance is found, the two ends can be permanently attached with glue. Slide the smaller tubing into the larger diameter tube. Visit our corporate site. The mailing tubes will be the body of the telescope with the smaller one sliding inside the larger one. However, the flexible pipe came slightly curved, a problem we thought would change with sufficient exterior pressure and/or enough time inside of the straight pipe. Thank you for signing up to Space. The cardboard tube still fell short of the PVC diameter, so we added cardboard spacers along the side. Space is part of Future US Inc, an international media group and leading digital publisher. Here is her first-person account of the process. These can be found in most office supply stores: Note that the focal lengths of the lenses are 1,350/152 = 8.88. Even a 4-foot telescope can be a handful to study the stars with; a 7-foot scope certainly requires assistance. By exchanging lenses, you can change the power of the telescope. Left: Inserting the objective lens into the flexible PVC pipe. We attempted a couple of different methods of securing the lens and the pipe. Keep pressure on the region until the glue has dried. A telescope's power, or magnification, has to do with its lenses. Our telescope builders and their completed project. When Italian astronomer Galileo Galilei heard rumors of the first practical telescope at the beginning of the 17th century, he was quick to craft his own version and turn it toward the heavens. However, lenses will likely be your most challenging item to purchase. Drill small holes around the outside of the inner tube, where the lens will be. In retrospect, we probably should have gone with the standard pipe and kept the excess around for future projects. Cut both of the tubes to that length with a knife or saw. Receive news and offers from our other brands? NY 10036. The nature of a Galilean telescope means that greater magnification requires longer length, which results in a more unwieldy telescope. We slid the eyepiece lens into the tube, working carefully to make sure that it was straight. Please deactivate your ad blocker in order to see our subscription offer. This article presents two methods of constructing a Galilean telescope — a cardboard tube created by the Galileo Project, which inspired our construction, and a PVC-pipe telescope, which we wound up using for our final project. Place the flat end of the eyepiece lens against the removable cap. The flexible PVC pipe was trickier, and the problem won't be resolved if you use a straight length of pipe. Magnification is determined by the focal length of the telescope divided by the focal length of the eyepiece. The project took them approximately an hour to complete. Get breaking space news and the latest updates on rocket launches, skywatching events and more! It is limited by its small field of view, but can inspire an even deeper study of the stars. Once the first spacer is dry, slide the objective lens in, with the second spacer against it. A Galilean telescope is, in essence, a tube with two lenses placed at either end. A telescoping mailing tube will have an inner tube that slides freely into the outer tube. Insert glue through the hole, spread it, and press until it is dry. PVC connectors, also purchasable at a hardware store, can serve to connect the two. At the other end is the objective lens, a concave-convex lens, which curves inward on one side and outward on the other. However, it results in a telescope with a magnification of 9x, while our final PVC telescope has a magnification of 20x, much like the telescope Galileo used to discover the four dominant moons of Jupiter. A coping saw will cut the cardboard clean and straight, which is important. There was a problem. Press the tube against the lens firmly until the glue is dry. Note: We chose to forgo standard PVC pipe of 1.5 inches simply because it only came in 10-foot lengths, while the flexible pipe did not. Note that the focal length of our lens are 2000/100 = 20, leading to a magnification of 20x. As such, we decided to switch the bulk of the body to a PVC pipe. Generally, the longer the focal length of the telescope, the more power it has, the larger the image and the smaller the field of view. Add the value of the focal lengths of the short and long lens together. To build a simple cardboard Galilean telescope with a magnification of approximately 9x, your materials will need to have the following specifications: Cardboard telescoping mailing tube, with an inner and outer tube that telescopes. Slide the lens and cap into the outer tube. Once the correct focusing distance is found, the two ends can be permanently attached with glue or tape. (Image credit: Galileo Project, Rice University). Receive mail from us on behalf of our trusted partners or sponsors? © While it won't be able to pick out the Galilean moons, a telescope with a focus of 9x should be able to see features on Earth's moon, including shallows from the plains, valleys and mountains.