PROJECTING THE SUN
The other technique used for solar viewing is projection. It requires no costly equipment and allows a group of people to view the Sun at one time. Aim your telescope at the Sun and affix a sheet of white cardboard behind the eyepiece, focusing until the image looks sharp.
Shield the projected solar image from any direct sunlight. Several observers can then gather around the telescope and study the Sun and its features. A projected solar diameter of 6 inches (150 mm) is easy to view and useful for sketching.
When aiming the telescope toward the Sun, never sight upward along the tube— instead, look at the scope's shadow on the ground. Cover the finder-scope's aperture so that it cannot accidentally burn you and no one is tempted to look through it. Never leave the telescope unattended—and if your group includes children, watch them like a hawk.
The heat of the Sun can ruin the optical cement in a compound eyepiece, so do not use your best eyepiece. Opt for a cheaper design such as a Huygenian or a Ramsden. If your scope's aperture exceeds
4 inches (100 mm), place an opaque mask with a circular cutout over the aperture to reduce it to 4 inches, or even less. This reduces the heat buildup inside the instrument.