- SP series eyepieces set the performance standard for modern telescope oculars. The proven 4-element Plössl design delivers edge-to-edge blackened elements the highest contrast images attainable. SP series eyepieces minimize spherical aberration, distortion, astigmatism and off-axis color white oversize optical elements afford the observer luxurious eye relief. Stray light is eliminated by the fold back rubber eyecups standard with every SP eyepiece and all but the lightest three models feature the security of rubber grips.