1.25 Inch Variable Polariser Filter

A dedicated 1.25 inch (31.7 mm) variable polarising filter designed exclusively for visual astronomy. Its robust aluminium housing encloses two matched polarising plates aligned orthogonally at default position; rotating the outer ring varies their angular relationship to achieve precise light attenuation from 1% to 40%. The optical elements are made from Schott B270-equivalent crown glass with dielectric anti-reflective coatings on all air-to-glass surfaces. Total thickness is 18 mm; thread specification is M28.5×0.6 external, matching most UK-sourced 1.25-inch eyepieces. Suitable for Dobsonians, refractors, and compound telescopes operating at f/4 to f/15. Not intended for imaging or solar use.