25mm Optical Flat, λ/20, Fused Silica

Precision fused silica optical flat, finished by classical continuous pitch polishing — the same method Lunt has refined over 25 years of building precision Fabry-Perot etalons for solar telescopes. Surface flatness measured power-included: total deviation including curvature, not power-removed. Diameter 25 mm Flatness (P-V) λ/20, power-included at 632.8 nm Material Fused silica Construction Single surface — one polished reference face Surface quality Better than 60-40 scratch-dig (typical) Surface roughness (RMS) Below 0.020 wave Clear aperture 90% of diameter (22 mm) Secondary surface Fine ground to suppress back-surface reflection Coating Uncoated Wavelength reference 632.8 nm (HeNe) Packaging Protective storage case included