Material L/A Extinction Angular Clear Aperture f a (mm) Outside Diameter f d (mm) L ±0.2 Ratio Field (mm) Calcite 2.5 <5x10 -5 14° -16° f 10 25.4 33 f 15 30 45.5 3 <5x10 -5 25°-28° f 10 25.4 38 f 15 30 53 α -BBO 2.5 <5x10 -6 14° -16° f 10 25.4 33 f 15 30 45.5 3 <5x10 -6 25°-28° f 10 25.4 38 f 15 30 53

