A 50-mm lens can be mounted inside of PVC tubing to make a refractor telescope.
The objective lens on a refractor telescope is found at one end of a long optical tube, while the opposite end holds the magnifying eyepiece called an ocular. A 50-millimeter objective lens captures about 50 times more light than the human eye, but the amount of magnification depends on the ocular. Building a telescope using PVC tubing, a 50-millimeter objective lens and an eyepiece will allow you to view all of the planets except Pluto, the moon and hundreds of deep-sky objects such as star clusters, nebulae and stars.
Instructions
1. Determine the focal length of the 50-millimeter objective lens by using a dark sheet of paper onto which you will focus the light of a flashlight. You can determine the focal length of a lens by measuring the distance between the lens and the focused bright light, where the light forms the smallest bright spot on the paper.
2. Select a 6-inch length of PVC tube with an inside diameter equal to the outside diameter of your eyepiece. Amateur telescope eyepieces come with outside diameters of 0.965 inch, 1.25 inch and 2 inches.
3. Cut the 1 inch length of PVC tube in half, around the circumference, so that you have two ½ inch lengths. This PVC tube should have an outside diameter of 50 millimeters. Glue each ½ inch length of tube, using silicon glue, to each side of the 50-millimeter lens and allow it to dry. This forms the objective lens assembly.
4. Cut the long PVC tube that will be the telescope's optical tube (this is the tube that has a 50-millimeter inside diameter) so that it is ½ inch longer than the focal length of the 50-millimeter lens. Spray paint the inside of the tube. After the paint has dried, slide the lens assembly into one end of the telescope optical tube, using light sandpaper to remove any material necessary to allow the assembly to slide easily.
5. When you are sure the assembly will fit, remove it, apply PVC glue to the outside edges and reposition the assembly within the telescope tube so that the edge of the lens assembly is flush with the telescope tube assembly. When the PVC glue is dry, use matte black paint to touch up any exposed PVC tubing, taking care to keep paint off of the lens by covering it with masking tape. Remove the tape when the paint has dried.
6. Slide the 6-inch length of PVC tube that will hold the eyepiece into a 1-inch length of PVC tube. Do not glue this piece. The outside diameter of the 6-inch piece of PVC should equal the inside diameter of the piece of 1-inch PVC. Slide the first 1-inch length of PVC into a second, larger 1-inch length of PVC. (The inside diameter will be equal to the outside diameter of the previous piece.)
7. Continue building up the diameter of the PVC tubes until you have built a large ring with an outside diameter of 50 millimeters. Insert the whole group into the 50-millimeter telescope tube and glue it in place with PVC glue. Do not glue the 6-inch-long piece that holds the eyepiece.
8. Focus the telescope by inserting the eyepiece into the 6-inch length of PVC tubing and then moving the PVC tube in or out. Refocus when you change eyepieces.
Tags: length tube, outside diameter, inside diameter, objective lens, tube that, 1-inch length