The Sky-Watcher Classic Dobsonian Telescope 153mm/1200mm (6"") has a ""paraboloidal"" primary mirror to eliminate spherical aberration and a four-arm, secondary- mirror bracket with fine supports (0.5mm thick), to reduce diffraction spikes and light loss. In addition, this models include a 2"" focuser with a 1.25"" adapter, allowing the use of either eyepiece size. This models also include the new feature-tension control handle..