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How to Make Solar Hydrogen Alpha Filters

Looking at the sun directly can cause damage to your eyes, especially during events such as a solar eclipse, where the light's rays are more concentrated. Using a special filter called a hydrogen alpha filter eliminates many of the dangerous rays while still allowing you to view the sun through a telescope. These filters can be very expensive, however. Making your own can save you money and allow you to view the sun through your telescope as long as you use the proper materials.

Things You'll Need

Measuring tape
Thin cardboard
Scissors
Glue
Double-sided tape
Solar film
Facial tissue

Instructions

- 1
  Cut a strip of cardboard about 1 inch wide and 2 feet long.
- 2
  Measure the distance around the end of the telescope. The lens will fit over the larger end of the telescope, not the eye piece.
- 3
  Cut the cardboard strip so it will fit tightly around the end of the telescope. Leave an extra 1/2 inch for overlap. Glue the strip into a circle.
- 4
  Wrap two or three more strips of cardboard around the first cardboard circle to make a thicker circle.
- 5
  Cut out two circles from the remaining cardboard to hold the film for the filter in place. One circle should match the diameter of the circle of cardboard you made and the other should match the lens size of your telescope.
- 6
  Cut out the inside of the circles to create rings. Leave a 1/4-inch ring of cardboard around the outer edges.
- 7
  Line one side of each ring with double-sided tape, and set them aside with the tape facing up so they don't stick to anything.
- 8
  Tape a facial tissue flat to your working surface. Lay a piece of solar film onto the facial tissue to keep it flat and clean.
- 9
  Hold one of the cardboard rings tape-side down over the solar film and lower it gently into place, taking care to keep the solar film flat. Press the ring gently down once the tape touches the solar film.
- 10
  Flip the solar film over so the cardboard ring is at the bottom and the empty side is facing up.
- 11
  Line up the second ring with the first ring through the solar film, and press it into place.
- 12
  Cut away any solar film that sticks out beyond the outside edges of the rings.
- 13
  Place a thin layer of glue around the edges of the cardboard circle you made with the strips of cardboard. Press the ringed solar film into place with the ring that is the same size as your lens facing the cardboard circle.
- 14
  Slide the cardboard circle over the end of your telescope and secure it in place with tape if needed.

Astronomy