This is a request for sources that the government can purchase PlaneWave™ Instruments CDK20 20” Optical Tube Assembly (OTA) and associated equipment. This is not a request for quotes. 1. The Space Science Program requires an optical telescope meeting the following minimum specifications: a. Aperture: 20” (500mm) minimum clear aperture. b. Optical Design: Dall-Kirkham (or Corrected Dall-Kirkham). c. Mount Compatibility: Compatible with Paramount MEII Robotic Telescope Mount. d. Imaging Device Compatibility: Compatible with ZWO ASI461MM Pro camera and Shelyak LHIRES III Spectrograph. e. Minimum Back Focus: 8” (203mm). f. Adapter Compatibility: Compatible with OpTec Gemini Focuser/Rotator and OpTec Perseus 4-Port Selector.