Eyepiece Orion Sirius Plossl 10mm Orion Telescopes & Binoculars · Sirius Plossl 10mm Key specifications Focal length10 mm Apparent FOV52 ° Barrel size1.25" All specifications Elements4 About 10mm 52-degree Plossl eyepiece; Orion's standard 4-element Plossl line.