Celestron C9 1/4-A XLT (CG-5) Schmidt-Cassegrain OTA
This magnificient optical tube from Celestron has an aperture of 9.25" that features Starbright XLT coatings. The C9 1/4-A XLT CG-5 OTA is a 9.25" OTA that excels at capturing every bit of light it can with its Schmidt-Cassegrain design. The coatings on the lens and the mirrors help reflect every bit of light possible as light moves through the optical internal components.
- 70 degree Field - Wide FOV for high and low magnifications
- Extendable twist-up eyecups - Good for eyeglass wearers
- Parfocal eyepiece - Little or no focusing is needed when changing from low to high power.
- Threaded barrels - Accept 2" Celestron thread-in filters.
- Shock resistant rubber covering - Scratch and dent resistant
- No slip grip - Designed for secure handling even in moist conditions
- Roll guard - Ergonomic contours prevent eyepiece from rolling off flat surfaces
- 28 mm clear aperture surface lens - For comfortable viewing
There are numerous features that Celestron has combined together that make the Starbright XLT coatings exceptional in the C9 1/4-A XLT OTA and its other Schmidt-Cassegrain optical tubes. First off, there are high quality multi-layer mirror coatings that are able to keep reflectivity balanced across the spectrum. Second, the anti-reflective coatings of Magnesium Flouride and Hafnium Dioxide give very wide bandpasses. Third, is the type of glass. Instead of using soda lime glass in the C9 1/4-A XLT OTA, water white glass is used instead since it has superior reflectivity right off the bat (90.5%). If you add in the anti-reflective coatings, reflectivity is reached to 97.4%! The graphs below shows how effective this can be and how much of an improvement Celestron has made from their original Starbright coatings.
Celestron’s excellent Schmidt-Cassegrain telescopes are compact and portable and represent the best all-purpose design for a wide variety of uses from terrestrial and deep sky viewing to astrophotography.
|Aperture||234.95 mm (9.25 in)|
|Dovetail Compatibility||CG-5 Mount|
|Eyepiece 1||25 mm (0.98 in)|
|Eyepiece 1 Magnification||94 x|
|Focal Length||2350 mm (93 in)|
|Highest Useful Magnification||555 x|
|Light Gathering Power||1127 x|
|Limiting Stellar Magnitude||14.4|
|Lowest Useful Magnification||34 x|
|Optical Coatings||StarBright / XLT|
|Optical Tube Length||22 in (559 mm)|
|Resolution (Dawes)||0.49 arc seconds|
|Resolution (Rayleigh)||0.59 arc seconds|
|Secondary Mirror Obstruction||3.35 in (85 mm)|
|Secondary Mirror Obstruction by Area||13 %|
|Secondary Mirror Obstruction by Diameter||36 %|