A Questar T-ring is the coupling ring that is used to connect your 35mm single lens reflex camera body to the Questar camera coupling sets used for astronomical and terrestrial photography with Questar telescopes and terrestrial spotting scopes. They do not work with non-Questar camera adapters.
Questar T-rings are internally threaded on one side to attach to the Praktica-type 42mm x 1mm pitch T-thread used on the Questar camera coupling set. The other side of the T-ring has the appropriate external thread pattern or bayonet mount to connect to your particular camera body. The 42mm x 1mm pitch male threads of the camera coupling set allow the coupling to be connected directly to camera bodies using a Pentax screw thread lens mount, so no Pentax screw thread T-ring is available or needed with the Questar photographic system.
Orientation of the camera horizontally or vertically for the best composition is done by adjusting a swivel mechanism on the camera coupling set itself.