11" Rowe-Ackermann Schmidt Astrograph (RASA 11) V2 Optical Tube Assembly (CGE Dovetail)
Item #: 91076 / 91076-CGL- Fast, wide-field 11” f/2.2 optical design with rare-earth glass for images free of false color, coma, and field curvature
- Large 43.3mm optimized image circle maintains pinpoint stars to the far corners of even the largest astroimaging sensors, while the usable field extends even further to 52mm for larger format sensors
- New Ultra-Stable Focus System (USFS) minimizes focus shift and mirror flop
- Integrated air-cooling system features a quiet, high-output 12V MagLev fan and vents with mesh filters to prevent dust ingress
- Common camera adapters (T-thread and M48) included for easy attachment to popular CCD and DSLR cameras
Overview
- Fast, wide-field 11” f/2.2 optical design with rare-earth glass for images free of false color, coma, and field curvature
- Large 43.3mm optimized image circle maintains pinpoint stars to the far corners of even the largest astroimaging sensors, while the usable field extends even further to 52mm for larger format sensors
- New Ultra-Stable Focus System (USFS) minimizes focus shift and mirror flop
- Integrated air-cooling system features a quiet, high-output 12V MagLev fan and vents with mesh filters to prevent dust ingress
- Common camera adapters (T-thread and M48) included for easy attachment to popular CCD and DSLR cameras
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Description
Capturing impressive deep-sky astroimages is easier than ever with Celestron’s Rowe-Ackermann Schmidt Astrograph (RASA) V2, the perfect companion to today’s top DSLR or astronomical CCD cameras. This fast, wide-field f/2.2 system allows for shorter exposure times compared to traditional f/10 astroimaging, without sacrificing resolution. Because shorter sub-exposure times are possible, your equatorial mount won’t need to accurately track over extended periods. The short focal length also lessens equatorial tracking demands. In many cases, autoguiding will not be required.
RASA 11 V2 builds on the legacy of Celestron’s Schmidt Cameras, which allowed astrophotographers to produce images with much shorter exposure times on film in the 1970s.
Today, with CCD sensor sizes as large as film or larger, the RASA 11 V2 offers a 43.3mm optimized image circle to capture pinpoint stars on the largest imaging chips. Optical performance for huge sensors with diagonals of up to 52mm wide is still excellent.
Combine this large image circle with a focal length of just 620mm and you have an instrument suitable for wide-field imaging, creating huge mosaics of the night sky, surveying, and even comet hunting.
Optical Performance
The RASA 11 V2 features optics with 4-element rare-earth glass for images free of false color and aberrations like coma and field curvature. The optical quality and spot size across the entire image circle are unprecedented for an astrograph in this price range—or even that of a much more expensive instrument. The design also provides minimal vignetting.
Advanced Features
RASA 11 V2 utilizes the new Ultra-Stable Focus System (USFS). At the heart of this system is a precision linear ball bearing. The bearing serves to minimize focus shift (unwanted lateral motion of the primary mirror during focusing which causes shifting of the image) and mirror flop (movement of the primary mirror when the telescope is pointing to different positions in the sky). The USFS is also compatible with the optional Celestron Focus Motor (#94155-A). The integrated 12V DC MagLev fan reduces cooldown time and provides optimal airflow through the dust filtered optical tube.
Engineered as a complete astroimaging system, every component of the RASA 11 V2 is optimized for peak performance with DSLR and astronomical CCD cameras. Down to the thickness of the glass used in the included fully-multicoated optical window or optional imaging filter, every component of the system has been taken into careful consideration to work together seamlessly. The Dovetail CGE bars on the top of the optical tube provides a connection for use of optional accessories like a guidescope.
Specifications
| Optical Tube Info: | |
|---|---|
| Optical Design: | Rowe-Ackermann Schmidt Astrograph |
| Aperture: | 279mm (11") |
| Focal Length: | 620mm (24.4") |
| Focal Ratio: | f/2.2 |
| Central obstruction diameter: | 114mm (4.48") (41% of aperture diameter) |
| Light Gathering Power (Compared to human eye): | 1588x |
| Resolution (Rayleigh): | 0.49 arc seconds |
| Resolution (Dawes): | 0.41 arc seconds |
| Image Circle: | 43.3mm (1.7") Ø , 4.0° |
| Useable field: | 52mm (2.04") Ø , 4.8° only minimal performance loss at edge of FOV |
| Wavelength range: | 400 - 700 nm |
| Spot size: | < 4.4 μm RMS across FOV |
| Optical Coatings: | StarBright XLT |
| Off-axis Illumination: | 83% at 21mm (0.82") off-axis |
| Optical Window: | 68mm (2.67") Ø |
| Back focus with included camera adapter: | 55mm (2.16") |
| Back focus from top of threaded collar: | 72.8mm (2.86") |
| Optical Tube: | Aluminum |
| Optical Tube Length: | 838.2mm (33") |
| Optical Tube Diameter: | 330.2mm (13") |
| Focuser: | Ultra-Stable Focus System |
| Finderscope: | Not included |
| Optical Tube Weight: | 43 lbs (19.5 kg) |
| Other Features: | Ventilation fan, dual dovetail mounting bars |
| Included items: | 42mm (1.65") T-thread camera adapter | 48mm (1.89") camera adapter | Dust cover | Fan battery pack |
| Dovetail: | CGE Dovetail Bar |
Videos
Accessories
FAQ
What is the heaviest recommend load for mounting a camera onto the RASA 11?
We recommend a load of no more than 33 lbs. at 5.0 inches away from the 11" Schmidt corrector.
I have a RASA 11, and I’m not certain if it is the original version or the V2 version. How can I tell the difference?
The RASA 11 V2 uses the Ultra-Stable Focus System, and therefore does not have mirror clutch knobs on the rear cell. The RASA 11 V2 also comes with the Celestron focus knob, not the FeatherTouch MircoFocuser.
Support & Downloads
| Manuals: |
|---|
| RASA 11" V2 Manual |
| Whitepaper RASA |
| Software & Firmware: |
| Periodic Error Correction Tool (PECTool) |
| Drawings: |
| RASA 11" Optical Tube Assembly Dimensional Drawings |
| Other Product Files: |
| Camera Adapter requirements |
| How to Align a Red Dot Finder to Your Telescope Video |
| Solar Safety Warning |
