The KSON KDB800160 optical tube assembly features a 800mm focal length x 160mm diameter primary mirror and features a heavy duty mirror cell with push / pull collimation screws. The primary mirror is fully aluminized with 92% reflectivity and has a Silicon Monoxide Quartz overcoat which protects the coating. The 160mm diameter mirror provides a resolving power of .72 arc seconds. The secondary mirror has an obstruction of approximately 25% linear (approximately 6% of the total area). The optical tube assembly is diffraction limited at λ4 (1/4 wave in Sodium light). The focuser is a 2″ format metal helical rack and pinion focuser with a 2″ to 1¼″ adapter to enable the use of larger 2″ eyepieces. The finderscope is KSON's electronic Finderscope which helps by getting the observer behind the telescope without losing the surrounding field of view when targeting objects. Included with the KSON KDB800160 are a 1¼″ 25mm Astroscopic eyepiece, a 1¼″ 10mm Kellner eyepiece and a 3x 2-element Achromatic Barlow lens. The 25mm is a 3 element, fully color corrected, modified Rank Kasspheric eyepiece with an apparent field of view of 52°. The 10mm Kellner eyepiece is a 4 element fully color corrected eyepiece with an apparent field of view of 52°. 1300mm x 160mm Optical Tube Assembly Easy to use Dobsonian mount in Handsome Matte Black Finish Diffraction limited Optical Tube Assembly (λ4) KSON Electronic Red Dot Finder Large 2″ Metal Helical Rack & Pinion Focuser 2″ to 1¼″ Adapter 25mm Astroscopic Eyepiece