Outfitted with an over-sized aperture, long effective focal length, and their proprietary StarBright XLT optical coatings, the Celestron C11-A XLT 11" f/10 Schmidt-Cassegrain Telescope provides power and portability. The coating system consists of anti-reflection coatings on the corrector plate, highly reflective index mirror coatings, and low-absorption/high-transmission glass components to ensure that the maximum amount of light is gathered and transmitted to the user's eye. This system ensures bright and clear high-contrast images with accurate color rendition across the entire visual spectrum without visible distortion at the edges. Celestron includes a standard 1.25" visual back to accept eyepieces and accessories such as the 40mm eyepiece and 90° diagonal supplied with the optical tube assembly (OTA). This OTA is offered here without a mount or tripod for users who already have a support system—just ensure the mount's payload capacity exceeds 27.5 pounds to safely carry the weight and that the mount has a Losmandy-style saddle to match the OTA's CGE mounting plate.
- 11" (279.4mm) aperture
- f/10 focal ratio
- 2800mm effective focal length
- Schmidt-Cassegrain design optical path
- StarBright XLT optical coatings
- Resolution: 0.5 arcsec (Rayleigh); 0.42 arcsec (Dawes)
- Secondary mirror obstruction: 3.75" (95 mm); 34% by diameter; 12% by area
- Maximizes light transmission through optical path
- Improves color rendition, contrast, sharpness, resolution, and brightness
- Broadband system provides flat wavelength transmission across the entire visual spectrum
- Multi-layer mirror coatings with layers of aluminum, SiO2 (quartz), and TiO2 (titanium dioxide)
- Multi-layer anti-reflective corrector plate coatings with layers of MgF2 (magnesium fluoride) and HfO2 (hafnium dioxide); hafnium has a wider band-pass than the commonly used titanium
- High-transmission water white glass corrector plate limits light loss due to internal absorption
- Optical tube only—mount and tripod required for proper use
- Supplied with CGE dovetail plate, which is compatible with Losmandy-style saddles
- Mount must have a payload capacity of over 27.5 pounds to safely support the OTA
- Visual back:
- Standard threads for Schmidt-Cassegrain telescope optical tubes
- 1.25" holder accepts 1.25" eyepieces and accessories
- Eyepiece:
- 1.25"-diameter barrel
- Accepts most 1.25" astronomical filters
- 40mm focal length produces 70x magnification
- Diagonal:
- 1.25"-diameter barrel
- 90° angle places head in comfortable viewing position when scope is aimed at or near the zenith
- Star diagonal corrects view horizontally, but not vertically
- Finderscope:
- 9x magnification
- 50mm aperture
- Mounting bracket included