The #905 Variable Polarizing Filter (1.25") greatly reduces glare in Moon observations through its two Polarizer filters mounted in a specially-machined cell. Rotate the thumbscrew on the side of the unit to adjust for varying lunar surface brightness related to Moon phases or scope magnifications. Variable settings of light transmissions range between 5% and 25% of their original value. The #905 inserts into the diagonal prism followed by the eyepiece. Accepts all 1.25" eyepieces.