C9.25 Optical Tube Assembly (CG-5 Dovetail)
Item #: 91025-XLT- 9.25" Schmidt-Cassegrain Optical Tube Assembly (OTA)
- Features Celestron's premium patented StarBright XLT optical coatings
- 2350mm focal length (f/10)
- Fastar compatible
- Tube constructed of durable and lightweight aluminum
- Includes: 25mm eyepiece (94x), 6x30 optical finderscope, star diagonal, 1.25” visual back, CG-5 dovetail bar
Overview
- 9.25" Schmidt-Cassegrain Optical Tube Assembly (OTA)
- Features Celestron's premium patented StarBright XLT optical coatings
- 2350mm focal length (f/10)
- Fastar compatible
- Tube constructed of durable and lightweight aluminum
- Includes: 25mm eyepiece (94x), 6x30 optical finderscope, star diagonal, 1.25” visual back, CG-5 dovetail bar
Includes These Celestron Technologies
Description
The Celestron C9.25 is an unusual size with its 9.25” aperture and 2350mm focal length, but many consider it to be the Goldilocks of optical tubes—not too big, not too small. This rugged aluminum optical tube is only 22 inches long and weighs just 20 pounds, making it easy to transport and set up. But the views are much more impressive than what you’d expect from such a compact instrument. The tube offers a focal ratio of f/10 with the added versatility of Fastar (see below).
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 Celestron C9.25 can be mounted on a multitude of computerized telescope mounts thanks to its CG-5 dovetail bar. This iconic optical tube provides the best balance of portability, handling ease, light gathering ability and price ever offered to the amateur astronomer.
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.
For more information about our Fastar technology, visit here.
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. For more information about our patented StarBright XLT coatings, visit here.
Specifications
| Optical Tube Info: | |
|---|---|
| Optical Design: | Schmidt-Cassegrain |
| Aperture: | 235mm (9.25") |
| Focal Length: | 2350mm (93") |
| Focal Ratio: | f/10 |
| Focal Length of Eyepiece 1: | 25mm (0.98") |
| Magnification of Eyepiece 1: | 94x |
| Finderscope: | 6x30 |
| Star Diagonal: | 1.25" Star Diagonal |
| Optical Tube: | Aluminum |
| Highest Useful Magnification: | 555x |
| Lowest Useful Magnification: | 34x |
| Limiting Stellar Magnitude: | 14.4 |
| Resolution (Rayleigh): | 0.59 arc seconds |
| Resolution (Dawes): | 0.49 arc seconds |
| Light Gathering Power (Compared to human eye): | 1127x |
| Secondary Mirror Obstruction: | 85mm (3.35") |
| Secondary Mirror Obstruction by Diameter: | 36% |
| Secondary Mirror Obstruction by Area: | 13% |
| Optical Coatings: | StarBright XLT |
| Optical Tube Length: | 559mm (22") |
| Optical Tube Diameter: | 271.78mm (10.7") |
| Optical Tube Weight: | 20 lbs (9.07 kg) |
| Dovetail: | CG-5 Dovetail bar |
Accessories
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FAQ
What is the heaviest recommend load for mounting a camera in the Fastar / HyperStar configuraton?
We recommend a load of no more than 25 lbs. at 4.2 inches away from the 9.25" Schmidt corrector.
Support & Downloads
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| SCT & EdgeHD Collimation Guide |
| Solar Safety Warning |
| What are the Sizes of Collimation Screws |
