The Optical (Flex)Tube Assembly
The SkyWatcher FlexTube 200P set up on the pad at GTCC’s Cline Observatory, before guests arrive
The SkyWatcher FlexTube 200P or Sky-Watcher’s 8″ Collapsible Dobsonian is an 8” f/6 Newtonian (203mm Aperture, 1200mm Focal Length), with the same optics as those found in Orion, Apertura, Zhumell, SkyWatcher classic, and GSO dobsonians. The main difference between this telescope and others of its size is the collapsible “FlexTube” functionality. This feature allows it to be stored more compactly than a traditional dobsonian. The OTA is extended by untightening three thumbscrews, pulling up the secondary mirror assembly until there’s a subtle click into place, and then retightening the thumbscrews.
The OTA measures 9.375” diameter and 44” long. It’s 33” when collapsed. The optical tube is 24 lbs, which is actually not lighter than the other 8” tubes (the missing mass of the optical tube is made up for by the large metal struts).
The secondary mirror assembly contains a finderscope mount, a 2” Crayford focuser, and a 1.88” secondary mirror. The primary mirror assembly carries the locking thumbscrews, collimation thumbscrews on the backside, and naturally the 8” primary mirror. The two assemblies are joined by three black metal rods.