Spectrum Telescope premium solar filter is safe to photograph or observe the sun when mounted on telescopes, spotting scopes, cameras or any optical device. It has a rating of Neutral Density 5, which blocks 99.999% of all light, including harmful IR and UV rays. The substrate is made of a highly reflective, Solar Glass and mounted into an aluminum cell. The filter slips over the sky end of your optical tube and is secured and centered with nylon thumb screws. Your solar filter will come packaged in a foam lined storage box and include instructions for proper use and care. When used properly, a natural yellow-orange image of the sun is viewed through your filter. Dependent on the size and strength of your optical device, you will be able to see sunspots, solar granulation (suns photosphere), eclipses, and planet transits. If you are unsure of the right size filter for your optical device please measure it or, contact us and we will be happy to help. Not sure this filter will fit? Measure your telescope: The filter slips over the sky end of the optical tube. Measure the outside diameter (OD), or widest distance across the optical tube of your telescope with a ruler, tape measurer, or caliper. This measurement should be equal to or between fit optical device 2” (51mm) to 2 3/8” (60mm)