How to Make a Barrel Telescope

Telescopes are a popular way to investigate space and geological regions in the distance. However, they also can be rather expensive. You can make a simple barrel telescope for a few dollars at home by following a few steps.

Things You'll Need

• 2 small rubber rings, slightly larger than the eyepiece lens (must be hollow in center)
• waterproof glue
• tube of insulating foam
• knife
• eyepiece lens with focal length between 20mm and 50mm
• short cardboard tube (e.g., paper towel roll)
• long cardboard tube (e.g., wrapping paper roll or poster tube)
• black cardboard or construction paper
• paper punch
• eyeglass lens (objective lens)
• 2 large rubber rings slightly larger in diameter than your objective lens
• cardboard
• black paint
• paintbrush

Instructions

Eyepiece

1. Paint the inside of the small cardboard tube with the black paint.

2. Allow the paint on the small tube to dry.

3. Sandwich the eyepiece lens between the two small rubber rings and glue them in place. The diameter of the rings needs to be just less than the diameter of the small cardboard tube so the lens can be slipped snugly inside.

4. Cut the tube of insulation foam lengthwise with the knife.

5. Pull the insulation foam tube apart at the cut point and insert one end the cardboard tube inside it. Your insulation tube should be large enough in diameter so that the seam comes back together with the cardboard tube inside the insulation tube. The insulation tube should cover about one-quarter to one-half of the cardboard tube.

6. Put several drops of glue between the cardboard tube and the insulation tube to hold them together.

7. Insert the tube of glue into the end of the cardboard tube that has no insulation on it, and place several drops of glue in a circle around the inside of the cardboard tube.

8. Slip the lens into the end of the cardboard tube that has no insulation tube around it until the lens reaches the spots of glue.

9. Gently press around the lens to secure the lens and tube with the glue.

Main Body

1. Paint the inside of the large cardboard tube black with the black paint.

2. Allow the paint on the large cardboard tube to dry.

3. Sandwich the objective lens between the two larger rubber rings and glue them together.

4. Insert the tube of glue into one end of the long cardboard tube and place several drops of glue in a circle around the inside of the cardboard tube.

5. Slip the objective lens into the end of the large cardboard tube until the lens reaches the spots of glue.

6. Gently press around the lens to secure the lens and tube with the glue.

7. Cut a circle of black construction paper just slightly larger than the diameter of your large cardboard tube.

8. Punch a hole in the center of the construction paper about 15mm to 20mm wide with the paper punch.

9. Cut a circle of cardboard about the same size as the construction paper circle.

10. Cut small tabs around the outside of the cardboard circle---do not cut deeper than the diameter of the large cardboard tube.

11. Bend the cardboard tabs over the end of the cardboard tube so the cardboard caps the tube.

12. Glue the tabs together if they overlap but don't glue the cap to the cardboard tube---you want to be able to take the cap on and off.

13. Cut a hole in the cardboard cap with the knife or paper punch and cut away until you have a space that is just less than the diameter of the large tube.

14. Place the black construction paper ring over the end of the large tube (the objective lens end).

15. Slip the cardboard cap over the objective lens end of the large tube to hold the construction paper ring in place.

Put the Telescope Together and Use

1. Insert the end of the small cardboard tube with the insulation foam on it into the non-eyepiece lens end of the larger tube. The insulation should hold the two tubes together but should still allow for some movement so you can focus the telescope.

2. Look through the small tube (your eyepiece) and pull or push until you have the right focus.

3. If needed, use a chair, table or other item as a stand for your telescope, since the minimal movement of your arm as you hold it may affect your ability to focus.

Tips & Warnings

• The black construction paper acts like the aperture for your telescope. You can make different rings with different sized holes in the center to allow for different light amounts. You can get the lens for the eyepiece and the objective lens from old glasses and cameras that don't work---you don't need to buy them, but you can take them in to have them cut to the right dimensions.

References

• Mid-level telescope-making directions

Resources

• Read this Article in Spanish
• Very basic telescope making at home