Celestron C11 11″ XLT Schmidt-Cassegrain Optical Tube Assembly


  • 11″ Schmidt-Cassegrain Optical Tube Assembly
  • Celestron’s premium StarBright XLT coatings
  • Aluminium Optical Tube
  • 2800 mm focal length (f/10)
  • 40 mm eyepiece included (70x)
  • 1.25″ visual back for use with 1.25″ accessories
  • 6×30 finderscope to help accurately find objects
  • Star diagonal provides more comfortable viewing position when observing objects that are high in the sky
  • CG-5/Vixen or CGE/Losmandy dovetail rail options
Starbright XLT Coatings
Category: SKU: 91067XLT Tag:


This 11″ aperture optical tube assembly (OTA) is an ideal choice if you want a very large aperture telescope that won’t break the bank. With its 11″ aperture the telescope is still not too large or too heavy to handle meaning that it can be used on a wide range of popular mid-range mounts such as Celestron’s Advanced VX. For astroimaging we would recommend the Celestron CGX or CGX-L mount.

The C11 features Celestron’s StarBright XLT coatings on the corrector plate for maximum light transmission. The telescope has a 2800mm focal length (f/10) making it a good overall performer on a range of celestial objects.

The telescope comes with a star diagonal for more comfortable viewing of high altitude objects and a 40mm Plossl eyepiece which gives 70x magnification. A 6×30 finderscope to help locate objects completes the package.

There are two dovetail bar versions of the C11 available – a CG-5/Vixen style and a wider CGE/Losmandy style. Both models are identical optically and with what is included in each package.

Optical DesignSchmidt-Cassegrain
Aperture279.4mm (11″)
Focal Length2800mm (110″)
Focal Ratiof/10
Focal Length of Eyepiece 140mm (1.57″)
Magnification of Eyepiece 170x
Star Diagonal1.25″ Star Diagonal
Optical TubeAluminium
Highest Useful Magnification660x
Lowest Useful Magnification40x
Limiting Stellar Magnitude14.7
Resolution (Rayleigh)0.5 arc seconds
Resolution (Dawes)0.42 arc seconds
Light Gathering Power (Compared to human eye)1593x
Secondary Mirror Obstruction95mm (3.75″)
Secondary Mirror Obstruction by Diameter34%
Secondary Mirror Obstruction by Area12%
Optical CoatingsStarBright XLT
Optical Tube Length610mm (24″)
Optical Tube Diameter312.42mm (12.4″)
Optical Tube Weight27.5 lbs (12.4 kg)
DovetailVixen/CG-5 Dovetail bar / CGE/Losmandy

Schmidt-Cassegrain Manual

Additional information

Weight10 kg
Dovetail Option


Celestron Technology


Optical Design