C6-A-XLT CG-5 Optical Tube Assembly

The Celestron C6-A OTA is a great multi-use optical tube with a 1500 mm focal length and a focal ratio of f/10. It offers 40% more light gathering than a 5” Cassegrain telescope. The Celestron C6-A features 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 Celestron C6-A can be mounted on a multitude of computerized telescope mounts thanks to its CG-5 dovetail bar. But it also works well when mounted on a basic manual altazimuth mount for night sky viewing or as a terrestrial spotting scope during the day.

The Celestron C6-A has the best balance of portability, handling ease, light gathering ability and price ever offered to the amateur astronomer. It is an advanced level instrument that is as easy to use as any intermediate level—and most entry level—telescopes.

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.