Celestron Edge HD Optical Tube AssembliesCelestron's Edge HD optical tubes have been developed to provide flat, well-corrected images for visual observation and imaging. In particular, the designers were aiming to meet the demands of large CCDs and Digital SLRs. At the same time they wanted to make the systems affordable. They have met all their objectives and Edge HD optics have gained widespread praise and several prestigious awards. The optics have been designed to reduce coma and field curvature and this is evident from the sharpness of images right across the whole field, but especially at the edges. At the same time, attention has been paid to mechanical aspects of the design. A new tension adjustment system for the primary mirror supports it at three additional points to eliminate mirror shift as the telescope tracks across the sky. A vent with a 60 micron filter at the rear of the cell helps the tube to cool more rapidly. The basic focal ratio of the OTA is f/10 but a new focal reducer will allow f/6.3 to be used, just like Celestron's conventional SCTs. Edge HD OTAs are also Fastar compatible which means they can be used with Starizona's Hyperstar for prime focus imaging at f/2. Existing Hyperstar owners just need a simple adaptor to transfer their Hyperstar to an Edge HD tube. Whether you are looking for your first catadioptiric optical tube or want to upgrade from a Schmidt-Cassegrain then Celestron's Edge HD optics are an excellent choice. All Edge HD OTAs are Fastar and Hyperstar compatible
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