Ideal for visual observation and astrophotography, the Vixen Optics SD81S II Telescope Optical Tube Assembly is designed for the amateur astronomer or photographer who wants to view and photograph the moon, planets, and deep sky objects. The SD81S II features FPL53 "super" extra-low dispersion (ED) glass in a fully multicoated apochromatic lens system that corrects for both spherical and chromatic aberrations, astigmatism, and off-axis comas. This correction creates a wide flat field of view without distortion and removes the blue-tinted halo effect for true high-contrast color transmission. It can accept both 2" and 1.25" eyepieces and accessories for visual use. Threads on the drawtube allow direct connection of T-rings and other camera mounts.

Included with the optical tube assembly (OTA) is a flip-mirror diagonal with dual 1.25" holders. The light path can be directed to the upper holder with the mirror in the Up position, and to the rear holder by flipping it down. For visual observation, the mirror can hold two eyepieces to allow easy changes from low to high magnification. When using it for imaging, the camera or imaging system is placed in the back, and an eyepiece can be attached at the top to check alignment and tracking between exposures. The OTA includes a mounting ring assembly and a Vixen-style dovetail plate to make it compatible with a wide variety of mounts. An integrated carry handle makes set up and break down safe and easy.