Meade 905 Variable Polarizer 1.25
#905 Variable Polarizing Filter (1.25")[For glare-reduction in observing the Moon the #905 Variable Polarizer includes two Polarizer filters mounted in a specially-machined cell. The #905 permits variable settings of the light transmission between 5% and 25%, to account for varying lunar surface brightness according to the phase of the Moon and the magnification and aperture of the telescope. The #905 inserts into the diagonal prism followed by the eyepiece. Accepts all 1.25" eyepieces.
Consists of two 30% transmission polarizing filters mounted in an adapter tube that fits into a 1.25" star diagonal. One filter is fixed at the bottom of the #905 tube and the other is mounted within the tube and is free to rotate. A 1.25" eyepiece slips into the top of the #905 tube and is held in place by a thumbscrew. The light transmission through the filter is varied over a 5% to 25% range by moving the lever shown at side of tube. The lever rotates the internal filter in relation to the fixed filter and eyepiece. The lever also acts as a thumbscrew to lock the orientation of the internal filter in place at any desired light transmission. The filters cannot be removed and used individually.
The #905 tube holds the eyepiece 1-7/8" above the star diagonal or focuser. Accordingly, it is designed for use in the star diagonals of Schmidt- and Maksutov-Cassegrain scopes that have a long back focus. The #905 will not work with reflectors and refractors as these scopes typically do not have enough focuser in-travel available to let the eyepiece reach focus.