The EdgeHD optics (Edge High Definition) combine the compact design of a Schmidt-Cassegrain with significantly improved imaging at the edge of the image. This optical system not only offers the properties of astrographs, but also produces completely undistorted, sharp images right up to the edge of the large visual and photographic field of view.

Not only is the coma outside the optical axis corrected - as with other "coma-free" optical designs available on the market - but also the field curvature!

Many optical systems are promoted as "astrographs"; however, they produce the coveted "pinpoint" star image along a curved image plane. On images taken with modern CCD cameras, the result is a noticeable field curvature that increases towards the edge of the image field and becomes stronger the larger the chip is; i.e. the stars remain round, but are blown up into small rings ("donuts") towards the edge.

With the Celestron Edge HD telescopes, this field curvature is corrected right up to the edge in addition to the coma, so that even images taken with large CCD chips are completely sharp, with a uniformly large star image across the entire chip - right into the corners of the image field.

This also significantly improves the resolution and limiting magnitude compared to competing optical systems with a similar aperture. The Celestron XLT multi-coating also helps the Edge HD optics to achieve a significant increase in performance compared to similar systems on the market.

The EdgeHD optics produce images three times flatter in the image field plane than a standard Schmidt-Cassegrain. The stars are imaged diffraction-limited across the entire chip of a Nikon D3 or Canon 5D !

Spec:

• Optical design: EdgeHD
  
• Optical coating: Starbright XLT (Fully multi-coated)
  
• Telescope aperture: 235mm (9.25")
  
• Focuser size (inches): 3.3" + 2" SC thread, 1.25"
  
• Tube (material): Aluminum
  
• Tube weight: 9.53kg
  
• Tube length: 22 in (559mm)
  
• Aperture ratio: f/10
  
• Resolution (DAWES): 0.49 arcseconds
  
• Resolution (RAYLEIGH): 0.59 arcseconds
• Focal length: 2350mm (93 in)
  
• Secondary mirror obstruction: 8.5cm
  
• Secondary mirror obstruction relative to diameter: 36.20%
  
• Secondary mirror obstruction relative to surface: 13.00%
  
• Limit size: 14.4
  
• Highest useful magnification: x555
  
• Light gathering capacity (compared to the human eye): x1127

Whats included:

1. Focal length eyepiece: 23mm
   
2. Incl. accessories: 9.25“ EdgeHD telescope with 3“ rail (Losmandy style) 9x50 finder, 2“ star diagonal, 1.25“ adapter, 23mm Luminos wide angle eyepiece.
   
3. Viewfinder: 9x50
   
4. Zenith prism: 2" with 1.25" adapter
   
5. Dovetail compatible: CGE (3“ Losmandy style)