How to Make a Spectrograph

Cut a slit in the end of the plastic tubing's 2-inch cap. Use a razor blade to cut through the plastic of the cap. Make the slit approximately 1 1/2 inches in length and centered on the cap.

Insert small pieces of heavy card stock or poster board at the top and bottom of the slit to hold the slit open. The slit allows light into the spectrograph. The ideal shape of the slit is 1 inch by 1 mm. The wider the slit, the wider the spectral line produced.

Roll the construction paper into a tube slightly less than 2 inches in diameter and place it into the 15-inch piece of black tubing. This will eliminate some of the reflection.

Place the rubber cap on the end of the tube and tighten it down with the hose clamp.

Cut a 2-inch ring from the card stock and then cut a smaller inner ring from the circular piece of card stock. Make the wall between the two rings 1/2 inch in thickness.

Glue the ring onto the center of the holographic diffraction grating. To achieve the best resolution possible, use a diffraction grating with 1000 lines per mm. Higher resolution provides the ability to separate spectral lines that lie close to one another.

Cut around the larger ring and fit the ring with the diffraction grating on it inside the tube. Use a piece of black electrical tape to hold the grating in place in the tube.

Place the digital camera at the exit hole of the spectrograph allow the spectra to shine on the focal plane of the spectrograph.