Celestron CGX Equatorial 800 HD Telescopes Whitepaper EdgeHD Optics - Page 12

Throughout the telescope-building process, we maintain a quality-assurance paper trail for each instrument. All test images are numbered and cross referenced. Should a telescope be returned to Celestron for service, we can consult our records to see how well it performed before it left our facility. Once a telescope has passed the FAT, we apply Loctite® to the set screws to permanently hold the alignment of the corrector plate. The instrument is then inspected carefully for cosmetic defects. It is cleaned and packaged for shipment to our dealers and customers. To your discerning eye-as an observer with experience-on a night with steady air and good seeing, a properly cooled EdgeHD performs exceptionally well on stars. You will see a round, clean Airy disk, a single well-defined diffraction ring, and symmetrical images inside and outside of focus. Every EdgeHD should resolve double stars to the Dawes limit, reveal subtle shadings in the belts of Jupiter, and reveal the Cassini Division in Saturn's rings. On deep-sky objects viewed with a high-quality eyepiece, star images appear sharp and well defined to the edge of the field of view. The EdgeHD reveals faint nebular details as fine as the sky quality at the observing site will allow. EdgeHD Field of View KAF-3200 KAF-8300 42 mm ∅ KAF-16803 FIGURE 12. In the Final Acceptance Test, the EdgeHD optics must demonstrate the ability to form sharp images at the center and in the corners of a Canon 5D Mark II full-frame digital SLR camera, with a sensor that measures 42mm corner-to-corner. APS-C DSLR Full-Frame DSLR KAI-10002 8. VISUAL OBSERVING WITH THE EDGEHD Because both the Celestron EdgeHD and our classic SCTs are diffraction-limited on-axis, their performance is essentially the same for high-magnification planetary or lunar viewing, splitting close double stars, or any other visual observing task that requires first-rate on-axis image quality. However, the EdgeHD outshines the classic SCT when it comes to observing deep-sky objects with the new generation of high-performance wide-field eyepieces. The classic SCT exhibits off-axis coma and field curvature which are absent from the EdgeHD design. Modern wide-field eyepieces, such as the 23mm Luminos, have an apparent field of view of 82 degrees, so they show you a larger swatch of the sky. Gone are the light-robbing radial flares of coma and annoying, out-of-focus peripheral images so sadly familiar to observers. With the EdgeHD, stars are crisp and sharp to the edge. The back of the EdgeHD 800 features an industry standard 2.00×24 tpi threaded flange. A large retaining ring firmly attaches the 1¼-inch visual back, and this accepts a 1¼-inch Star Diagonal that will accept any standard 1¼-inch eyepiece. The EdgeHD 925, 1100, and 1400 feature a heavy-duty flange with a 3.290×16 tpi threaded flange. This oversize flange allows you to attach heavy CCD cameras and digital SLR cameras. For visual observing, use the adapter plate supplied with each telescope to attach the Visual Back. The 2-inch Diagonal (also supplied with these telescopes) accepts eyepieces with 1¼-inch and 2-inch barrels. FIGURE 13. EdgeHD telescopes are designed to provide good images across a flat 42mm diameter field of view. Compare this with the size of a variety of image sensor formats. The popular APS-C digital SLR format fits easily. The full-frame DSLR format is fully covered. EdgeHD even covers the 36.8mm square KAF-16803 format remarkably well. 12 I The Celestron EdgeHD