Used 2.5" (63mm) Helios Solar Glass Filter. Fits Optical Tube Diameter 2 1/8" (54mm) to 2 3/8" (59mm). SF250U
This premium solar filter is safe to photograph or view the sun when mounted on a telescope, view finder, spotting scope, etc. It is rated ND5 so 99.999% of the sunlight is blocked. The aperture is made of a high quality, reflective coated, Helios Solar Glass, and mounted into an aluminum outer cell. The filter slips over the sky end of your optical tube. It is secured and centered to the optical tube with a nylon thumb screw and felt tabs. It is packaged in a foam lined storage box, and included are instructions for use and care. A natural yellow-orange image of the sun is viewed through the filter. You will be able to see sun spots, surface granulation, eclipses, and planet transits. If you are not sure this is the right size filter for your optical device please click on FAQ and follow the directions for, "How do I find the right size filter to order?"