SWAN: how many comparable EPs at this price? The Swan eyepieces are super wide angle designs with 72° apparent field of view. They use simple but sophisticated five-lens optical systems for generally higher contrast than the more complicated optical designs used in some other super wide angle eyepieces that use up to eight lenses. All lenses are fully multicoated for high light transmission. Lens edges and internal field stops are blackened to reduce internal reflections and improve contrast. The eyepiecerubber grip ring is useful for safer handling of the heavier 2” eyepieces in cold weather when wearing gloves. The eyepieces have soft roll down rubber eyecups for eyeglass use. They can be used for all types of observing, with all telescope types, but they are recommended for use with focal ratios up to f/6 and above. Dust caps are provided for both ends of each eyepiece. A soft protective drawstring-equipped velvet storage bag is standard equipment with each. This 5-element super-wide angle 15mm SWAN EP’s panoramic views at 72 deg. F.O.V. will leave you speechless! For day and night! A very useful focal length which every user should have. Your Window on the Sky! • Outstanding super-wide field of view: 72° F.O.V. • Fully Multicoated lenses for excellent transmittance. • Reduced chromatic aberration. • Improved sharpness and contrast throughout the field. Impressive Performances • Internally fully blackened (lens edges and internal spacers). • No flaring or ghosting on high-contrast objects. • Parfocal. Comfortable • Soft rubber eyecup. • Long eye-relief: 14mm. • No internal reflections, kidney beaning, pin-cushion or other distortions. Terrific Fit and Finish • High-resistance anodized black barrel. • Smooth design for no hook up in your focuser. • Threaded for filters’ usage. 　 Internally baffled, All lenses' edges and internal spacers blackened, Fully multicoated Model SWAN 15 Focal Length 15mm Lens Structure (#Elements/#Groups) 5/4 Field of View 72 Eye Relief 14mm Barrel 1.25" Coating FMC Parfocal Yes Weight 90g