Like most Schmidt-Cassegrain telescopes, the Celestron C9.25-A XLT has a focal ratio of f/10, meaning it is quite suitable for looking at many different celestial objects without the annoying optical disturbances of pure refractors and reflectors like chromatic aberration. The StarBright XLT coatings bring excellent light transmission from the corrector to the eyepiece ensuring as little light is wasted as possible to produce the brightness images. Since Schmidt-Cassegrain designs use both corrective plates and primary mirrors (aspects of both refractors and reflectors), they naturally can physically only have a slow focal ratio but also accommodate many accessories that can change it, making it even more suitable for faster CCD imaging or viewing. For instance, the focal reducer by Celestron (NOT INCLUDED, PURCHASED SEPARATELY) brings the focal ratio to f/6.3, making lower surface brightness objects look more impressive. This also assists in astrophotography because faster focal ratios are more efficient when taking exposures with larger pixel sizes since slower focal ratios tend to take too long for unsatisfying results (such as possible blooming). For visual astronomy, a 6x30 finderscope, 25mm eyepiece eyepiece, 1.25" star diagonal, and 1.25" visual back are all included with the purchase.
Celestron's high quality Schmidt Cassegrain design, available in an Optical Tube Assembly. These are the same quality as the tube assemblies that come with their telescope packages, but without the mount. This is a great way to upgrade, without the need to buy the whole telescope system.
This is the Optical Tube Assembly, without the mount.
- 9.25" Schmidt-Cassegrain, 2350mm focal length (f/11) Aluminum Optical Tube.
- Starbright XLT Multi-Coatings.
- 6x30 finderscope.
- 25mm eyepiece (94x).
- 1-1/4", star diagonal.
- 1-1/4" visual back.
- Dovetail slide bar for Celestron's CG-5 Mount.
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.
|Name||Celestron - C9.25-A XLT (CG-5) Optical Tube Assembly|
|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 %|