Sky-Watcher Skymax-90T, 90mm (3.5"") f/1250 Maksutov-Cassegrain Optical tube Assembly. The Sky-Watcher SKYMAX Maksutov-Cassegrains are the ultimatetake-anywhere' telescopes. They are also ideal if working space is limited. Despite their small dimensions they pack a powerful punch. Their High-Resolution, diffraction limited optical systems are multi-coated to maximize contrast and image sharpness. The Skymax Maksutov' come in apertures of 90mm, 102mm and 127mm, and are available either complete with equatorial mounts and tripods, or as tube assemblies only, which can be mounted onto a standard photographic tripod. Whether your requirement is for terrestrial or astronomical use, these compact scopes are the perfect companion. Tube material: Aluminium. Please note, the is an Optical Tube Assembly only, mount and tripod are available separately.