Celestron C-11 A is 11.0"/279mm Aluminum Schmidt-Cassegrain Telescope Optical Tube Assembly (2800mm f/10.0)Now you can have your own a la carte assemblage of your preferred optical tube and mount. Celestron-C11A Schmidt-Cassegrain Telescopes utilize the multicoated Starbright coatings group. Highly reflective coatings are used on the mirrors, with anti-reflective coatings employed on the correcting lens for increases in light transmission. Celestron's optical systems internal baffling ensures the highest contrast levels. To provide consistent customer satisfaction and high performance, CelestronC11-A Optical Assembly utilizes the same superior optics regardless of their size or configuration.

• 91067-XLT: Celestron C-11A Schmidt Cassegrain Telescope 11" Optical Tube w/ Star Bright XLT Coating, w/ dovetail slide bar made to fit Celestron CG-5 Mount
• 91036-XLT: Celestron C-11 A Schmidt-Cassegrain Optical Tube w/ StarBright XLT Coatings

With StarBright XLT Optical System Design you'll see the light.One of the most important factors in the evaluation of a Schmidt-Cassegrain telescope 's optical system performance is its transmission - the percentage of incoming light that reaches the focal plane. The design of the XLT System accomplishes two crucial objectives: Develop a coating system that is optimized for visual use and for CCD/Photographic imaging.There are three major components that make up Celestron StarBrightXLT high transmission optical system design:1. Unique enhanced multi-layer mirror coatings:Celestron mirror coatings are made from precise layers of Al (Aluminum), SiO2 (quartz) and TiO2 (Titanium Dioxide). Reflectivity is fairly flat across the spectrum, optimizing it for both CCD imaging and visual use. 2. Multi-layer anti-reflective coatings:Coatings are made from precise layers of MgF2 (Magnesium Fluoride), and HfO2 (Hafnium Dioxide). Hafnium gives a wider band pass than Titanium, used in comparable coatings.3. High Transmission Water White glass :Celestron Schmidt-Cassegrain optical systems with optional StarBright XLT coatings use Water White glass instead of Soda Lime glass for the corrector lens. Water White glass transmits about 90.5% of light without anti-reflective coatings. That is 3.5% better transmission than uncoated Soda Lime glass. When Water White glass is used in conjunction with StarBright - XLT 's anti-reflective coatings, the average light transmission reaches 97.4% - an 8% improvement!These three components of Celestron StarBright XLT coatings result in one of the finest coatings available. The peak light transmission for the systems is 89% at 520 nm. The overall system transmission is 83.5% averaged over the spectrum from 400 to 750 nm.

Specifications for Celestron-C-11-A Telescopes:

Optical Design:		Schmidt-Cassegrain
Optical Diameter:		11.0" (279mm)
Focal Length:		110.2" (2800mm)
Focal Ratio:		f/10
Maximum Useful Magnification:		660x
Resolving Power (arc seconds):		0.41
Optical Coatings:		Starbright or StarBright-XLT coatings
Optical Tube Dimensions:		24.0" (61.0 cm) Long
Eyepiece Barrel Diameter:		1.25"
Finderscope:		9x50mm
Weight:		27.50 lb (12.48 kg)

Features of CelestronC11A Telescopes:

• Limiting stellar magnitude of 14.7
• Focus as close as 60' (18 m) for terrestial viewing
• Secondary mirror obstruction of 13.2%(by area)
• Aluminum tube materials

Package Contents:

• Celestron-C 11" A Telescope
• 9x50mm Finderscope
• 26mm (107x) Plossl Eyepiece (1.25")
• Star Diagonal and Visual Back
• Dovetail Slide Bar