Things You'll Need
7 1/2-inch paper tube, 2-inch diameter
7 1/2-inch paper towel roll, 1 1/2-inch diameter
1 1/2-inch double convex lens, 30-cm focal length
1 1/2-inch double convex lens, 5-cm focal length
Clear acetate sheet
You can teach about light refraction with a homemade working telescope or simply enjoy a 'scope-sculpting craft project with younger kids. Kids can create the working telescope with a pair of double convex lenses, purchased for about $10. The telescope is simple enough to put together within a single class period and provides hours of learning opportunities afterwards.
A Working Paper Roll Telescope
Create two cardboard holders for the lenses. Trace around each lens on the cardboard to create two circles. Measure outward a little over 1/2 inch on one circle pattern, and 1/4 inch on the other circle pattern. Draw a second circle around each patter with these new wider diameters. This creates two ring patterns. Cut out the rings of cardboard, taking care to keep them intact.
Place the lenses in the cardboard holders. Apply a small amount of white glue to the outside edge of each lens. Squeeze each lens into the center of each cardboard ring. The long focal lens goes into the ring with a wider diameter. Check that both lenses are perfectly even with the cardboard. Allow the glue to dry.
Glue the lenses in place. Apply a small amount of white glue around the edge of the larger lens holder. Press this holder -- with lens -- against one end of the paper tube with a wider diameter. The cardboard holder should be just larger than the diameter of the paper tube. Repeat this process with the smaller tube and other cardboard holder. Allow the glue to dry.
Slide the open end of the smaller cardboard tube inside the open end of the larger diameter tube. Hold the short focal lens to your eye. Try to focus on something in the distance by sliding the tubes along one another. If you find that the smaller tube is too long to bring the object into focus, cut the length of the smaller tube down an inch or two.
A Pretend Paper Roll Telescope
Spread out some newspaper for your work area. Prepare a small bowl of water for dipping your paint brushes in.
Select a paper towel roll of any desired length. Cut a slit halfway through the cardboard roll roughly a couple of inches from one end. An adult should complete this part of the project with a box cutter.
Hold one end of the paper roll against a sheet of acetate paper. Trace around the end with a marker to create a circle template.
Draw a horizontal rectangle over the circle, with a half-moon cutout formed by the top half of the circle. Give the rectangle a length that is roughly a couple of inches longer than the circle's diameter. This creates short tabs on either side of the circle.
Paint a landscape scene inside the acetate circle. Make your scene simple, but it can be anything. This is a good step for the kids to complete. Allow the paint to dry -- less than an hour.
Cut out the entire acetate circle with rectangle tabs. This becomes the slide picture for your pretend telescope.
Slide the acetate circle into the slit you cut through the paper roll. The tabs will stick out, making it easier to remove the slide and replace with another as needed. Look through your new telescope.
Paint your cardboard tubes in fun colors to complete the look of your telescope. Check out the wide variety of lenses you can try in your telescope. Two double convex lenses are only the simplest option.
Handle the telescope with care. Paper tubes are not very strong.