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How to Make a Galilean Telescope

The Galilean telescope, named after famed astronomer Galileo Galilei, is a refracting telescope which has the ability to magnify objects up to 30 times. This type of telescope consists of a convex objective lens, which serves to magnify the object, and a concave ocular lens, which serves as the eyepiece. Combining these lenses ensures an image that is an upright, magnified version of the object, making this telescope an ideal tool to explore distant objects. A Galilean telescope can be constructed at home, with the right materials and know-how.

Things You'll Need

Cardboard mailing tube with cap
Drawtube (e.g. cardboard paper towel roll)
Concave lens
Convex lens
Cardboard box
Pencil
Scissors

Instructions

- 1
  Make a circular hole in the cap of the mailing tube with approximately the same diameter as the concave lens, which will serve as the objective lens.
- 2
  Glue or tape the concave lens to the cap, with the concave side of the lens facing out of the mailing tube, towards the objects you would like to view. Ensure the lens is properly centered.
- 3
  Use the mailing tube to trace a circle on the cardboard box. Do the same with the drawtube, with the circle from the smaller drawtube located inside the circle from the larger mailing tube, creating a ring. With scissors, cut just outside the outline made from the drawtube, and just inside the outline from the mailing tube. This results in a cardboard ring which can be placed around the drawtube, and fit inside the mailing tube. Repeat this process twice, producing two identical cardboard rings.
- 4
  Glue one ring to the end of the drawtube. Once the glue has dried, insert the drawtube into the open end of the mailing tube, making sure that a portion of the drawtube emerges from the mailing tube.
  
  Slide the second ring down the protruding end of the drawtube. Once the ring is at the end of the mailing tube, glue the ring in place. Once the glue is dry, this ring should allow the drawtube to slide easily and accurately within the main tube.
- 5
  Insert the convex lens (also called the ocular lens) into the drawtube, with the convex side of the lens facing out of the drawtube. Tape or glue the lens securely in place.

Astronomy