Celestron CGX Equatorial 800 HD Telescopes Whitepaper EdgeHD Optics - Page 14

Celestron's EdgeHD: The Versatile CImealegsitnrognP'slaEtdfogremHD: The Versatile Imaging Platform EdgeHD 800 5.25 inches 133.35±0.5 mm Small T-Adapter Camera Adapter Digital SLR EdgeHD 925, 1100, and 1400 5.75 inches 146.05±0.5 mm Reducing Ring Small T-Adapter T-to-1.25" Adapter Webcam Large T-Adapter T-Ring Adapter Digital SLR Large T-Adapter T-to-C Adapter Astro Video Camera Large T-Adapter T-system Spacer CCD Camera FIGURE 14. It is easy to position your digital SLR camera, an astronomical CCD camera, a high-performance video camera, or an inexpensive webcam at the focus plane of your EdgeHD telescope. For the sharpest wide-field imaging, your goal is to place the sensor 5.25 inches behind the rear flange of the EdgeHD 800, or 5.75 inches behind the rear flange of the EdgeHD 925, 1100, and1400. For those who wish to make images with a faster focal ratio than EdgeHD 1100's ƒ/10 or the EdgeHD 1400's ƒ/11, we designed a five-element 0.7× reducer lens for each of these EdgeHD telescopes. (For more information, see Appendix B.) The Reducer Lens 0.7× for the EdgeHD 1100 is item #94241; for the 14-inch, item #94240. (The newly-released EdgeHD 800 Focal Reducer is item #94242.) The reducer lens attaches directly to the 3.290×16 tpi threaded baffle tube lock nut on the back of the telescope. Since the back focus distance for the 1100 and 1400 reducer lens is 5.75 inches (146.05mm), you can use the same T-Adapter and camera T-Ring you would use for imaging at the ƒ/10 or ƒ/11 focus. The linear field of view is still 42mm diameter, but the angular field is 43% larger, and exposure times drop by a factor of two. For super-fast, super-wide imaging, the EdgeHD telescope series supports Starizona's Hyperstar lens. Mounted on the corrector plate in place of the secondary mirror, the Hyperstar provides an ƒ/1.9 focal ratio on the EdgeHD 1400, and ƒ/2.0 or ƒ/2.1 on the 800, 925, and 1100. Covering a 27mm diameter field of view, the Hyperstar is a perfect match for APS-C format digital SLR cameras. Because of the short focal length and fast focal ratio, sub-exposures are just a minutes. With a solid, polar-aligned equatorial mount, guiding seldom necessary. Of course, the focal length of any EdgeHD telescope can be extended using a Barlow lens such as the Celestron 2x X-Cel LX (item #93529) or 3x X-Cel LX (item #93428). Using a Barlow, imagers can reach the desirable f/22 to f/32 range for ultra-high-resolution lunar and planetary imaging. In summary, the Celestron EdgeHD telescopes provide a flexible platform for imaging. You can work at the normal ƒ/10 or ƒ/11 Cassegrain focus for seeing-limited deep-sky images or add the reducer lens for wider fields and shorter exposure times. With a Hyperstar, you can grab wide-field, deep-sky images in mere minutes. And finally, you can extend the focus to capture fine lunar and planetary images with a quality Barlow lens. When you buy an EdgeHD telescope, you're getting an imaging platform that covers all the bases, from fast, wide-field imaging to high-resolution imaging of the moon and planets. 14 I The Celestron EdgeHD