Celestron C11 Cassegrain OTA CGE

The Celestron C11-A packs serious light gathering ability into a rugged aluminum optical tube. At only 24 inches long and weighing just 27.5 pounds, this telescope is still portable enough to be taken to dark skies and set up by a single person. It’s an ideal instrument for serious astrophotography.

The Celestron C11 provides excellent, high-contrast views and can perform at very high magnifications. It is equipped with Celestron’s patented StarBright® XLT optical coatings, which visibly increase contrast and light transmission for brighter deep space images and shorter exposure times. With StarBright XLT, you’ll be able to discern subtle details while viewing the Moon and planets as well as faint galaxies and nebulae.

The tube offers a focal ratio of f/10 with the added versatility of Fastar (see below). You can also pair it with the f/6.3 focal reducer for even more astroimaging options.

The Celestron C11-A can be mounted on a multitude of computerized telescope mounts thanks to its CGEM-style dovetail bar. This flagship optical tube is sure to take your visual observing or imaging to the next level.

Fastar Technology

In 1997, CCDs were making a name for themselves in the astrophotography world, quickly supplanting traditional film photography thanks to their speed and convenience. This was the year that Celestron joined forces with the Santa Barbara Instruments Group (SBIG) to produce Fastar, a revolutionary add-on to Celestron’s hugely popular Schmidt-Cassegrain (SCT) optical system.

With Fastar, the SCT’s secondary mirror can be removed and replaced with a field-flattening lens assembly (sold separately by third party manufacturers) so that a CCD camera can be used in the front of the telescope at the f/2 focus of the instrument’s primary mirror. The potential of the Fastar system is staggering: exposures are 25 times shorter than if the camera was placed at the instrument’s native f/10 focus. Imagers can capture galaxies and nebulae with exposures of just 30 seconds. 

StarBright XLT coatings

StarBright XLT is Celestron’s revolutionary optical coating system. It consistently outperforms all other coatings in the commercial telescope market. There are three major components that make up our StarBright XLT high-transmission optical system design:

• Unique enhanced multi-layer mirror coatings made from precise layers of aluminum, SiO2 (quartz), TiO2 (titanium dioxide), and SiO2 (silicon dioxide). Reflectivity is fairly flat across the spectrum, optimizing it for both imaging and visual observing.
• Multi-layer anti-reflective coatings made from precise layers of MgF2 (magnesium fluoride) and HfO2 (hafnium dioxide). Hafnium—a rare element that costs nearly $2,000 per kilogram—gives us a wider band pass than the titanium used in competing coatings.
• High-transmission water white glass is used instead of soda lime glass for the corrector lens. Water white glass transmits about 90.5% of light without anti-reflective coatings; that’s 3.5% better than uncoated soda lime glass. When water white glass is used in conjunction with StarBright XLT’s anti-reflective coatings, the average transmission reaches an astonishing 97.4.
  
  

These three components make StarBright XLT one of the finest coatings available.