Celestron CGEM 1100 HD Computerized Telescope EdgeHD Optics Manual - Page 6

A telescope is an instrument that collects and focuses light. The nature of the optical design determines how the light is focused. Some telescopes, known as refractors, use lenses. Other telescopes, known as reflectors, use mirrors. The EdgeHD optical system (Apanatic Schmidt) uses a combination of mirrors and lenses and is referred to as a compound or catadioptric telescope. This unique design offers large-diameter optics while maintaining very short tube lengths, making them extremely portable. The EdgeHD system consists of a zero power corrector plate, a spherical primary mirror, and a secondary mirror along with a set of field flattening lens integrated into the baffle tube . Once light rays enter the optical system, they travel the length of the optical tube three times. The optics of an EdgeHD telescopes have Starbright XLT coatings - enhanced multi-layer coatings on the primary and secondary mirrors for increased reflectivity and a fully coated corrector for the finest anti-reflection characteristics. Inside the optical tube, a black tube extends out from the center hole in the primary mirror. This is the primary baffle tube and it prevents stray light from passing through to the eyepiece or camera. Figure 2-1 A cutaway view of the light path of the EdgeHD optical design Image Orientation The image orientation changes depending on how the eyepiece is inserted into the telescope. When using the star diagonal, the image is right-side-up, but reversed from left-to-right (i.e., mirror image). If inserting the eyepiece directly into the visual back (i.e., without the star diagonal), the image is upside-down and reversed from left-to-right (i.e., inverted). This is normal for the EdgeHD design. Actual image orientation as seen with the unaided eye Reversed from left to right, as viewed with a Star Diagonal Figure 2-2 6 Inverted image, as viewed with the eyepiece directly in telescope