Q. "Should I buy the original Celestron SCT model or the new Celestron EDGE HD?".
A. The regular SCT was not designed for photography, though it does work very well when used with a 'small' sensor camera for lunar/planetary imaging. A combined f6.3 reducer/flattener is available for larger sensors but it is a compromise because flatteners and reducers perform different functions and the ideal position for the flattening component is inside the telescope, not outside. With the EDGE HD series Celestron have produced 'separate' flatteners and reducers for each model. The flattener is pre-fitted fitted inside the telescope - in the optimum position - and a dedicated reducer is available for fitting to the rear. This approach provides the large evenly illuminated flat field. There are some other mechanical benefits but they are minor compared to the EDGE HD optics. So, if you are an eye-to-eyepiece visual astronomer, or an imager using a camera with a small sensor, then the original SCT telescope will serve you well. If you are an imager using a sensor (up to APS-C size) then you are on the right page. The EDGE HD is a better suited to your needs.
Introducing the new Celestron Edge HD
- Visibly Sharper Images
- Coma-free, flat-field optics
- Enhanced Mechanical Features
- Fastar® Compatible
EdgeHD is an Aplanatic Schmidt telescope designed to produce aberration-free images across a wide visual and photographic field of view. The optical system was designed to reduce more than just off-axis star coma, but also to give an astrograph quality flat focal plane all the way to the edge of the field of view.
Celestron Edge HD White Paper pdf (6.5mb)
True Astrograph Quality
Many optical designs that advertise themselves as "astrograph" quality actually only produce pinpoint stars across a curved focal plane. While this may be acceptable for visual observing, stars will appear out of focus at the edge when used with a flat chip sensor of a digital camera. EdgeHD optics produce a focal plane more than three-times flatter than a standard Schmidt Cassegrain telescope and dramatically flatter than other competing coma-free designs. This guarantees you visibly sharp stars across some of the largest CCD chips available today.
Superior edge performance not only creates rounder, more pleasing stars but actually improves the resolution and limiting magnitude when compared to telescopes of equal aperture. Starbright XLT® Coatings coupled with Celestron's StarBright XLT coating group on every surface, EdgeHD optics gives you maximum light throughput across the widest visual and photographic spectrum.
In addition to Celestron’s new optimized optical design, the EdgeHD tube has been redesigned to make sure you get the most from your optics each and every night.
Mirror Clutches - Flexible tension clutches hold the mirror in place and reduce image shift when rotating the tube around the mount. The flexible rods allow the mirror to be held in place without putting any force or pressure on the mirror assembly, keeping the image centered in the eyepiece (or chip).
Tube Vents - Cooling vents located on the rear cell allow hot air to be released from behind the primary mirror. Each vent has an integrated 60 micron micro-mesh filter guaranteed to let warm air out without letting dust in.
Fastar Versatility - The EdgeHD is the most versatile imaging scope available today. At its native f/10 you can achieve the image scale necessary to capture the smallest of deep sky objects. With the optional reducer lens (coming soon) you can increase your field of view without sacrificing optical performance. A barlow gives you the added power for high resolution planetary, lunar and solar imaging. And of course all EdgeHD optical tubes are Fastar® compatible for ultra fast f/2 wide field imaging. Each tube has been fitted with a removable secondary mirror and are opto-mechanically aligned on a laser bench to ensure they are axially symmetric in any configuration.
All Celestron EDGE HD telescopes are fitted with the larger CGE (Losmandy-type) dovetail except for the 8-inch model which can be supplied with a Vixen-type dovetail if requested.