The Sky-Watcher Dobsonian Telescope 153mm/1200mm (6") (F/ratio: f/7.8) have 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 model includes a 2" focuser with a 1.25" adapter, allowing the use of either eyepiece size. This model also includes the new feature – tension control handle.
The object of the Sky-Watcher Tension Control Handle invention (US Patent No. 6,940,642) is to provide a tension adjuster that users can easily turn to add or reduce tension, thereby increasing or decreasing the friction between the optical tube and the sideboard of the mount. By providing such a tension adjuster, the telescope does not need to be balanced in order to stay in position. The tension adjuster can be tightened such that the optical tube can stay in a position but can still be moved when prompted to adjust the position of the optical tube. Alternatively, the tension adjuster can be completely tightened to lock the optical tube in position. It will fit in the boot of most hatchbacks or saloon cars, fits easily across the back seat of most cars.
Set up is very simple. The tube slots onto the base from above. Molded side bearings on the tube itself rest on four saddle side bearings on the base. Two tension handles are tightened on either side of the base. These should be screwed all the way in until there is some resistance in the tube’s forward / backward motion. You’re then ready to observe!