Celestron 11" RASA V2 OTA - CGE Dovetail

The f/2.2 Rowe-Ackermann Design: 1588x More Light Gathering Power

The core of the RASA 11 V2 is its f/2.2 focal ratio, a speed that fundamentally changes the imaging process. This allows you to collect the same amount of signal in minutes as a traditional f/10 Schmidt-Cassegrain collects in hours. The immediate benefit is that tracking and autoguiding become far less critical; many targets can be captured with short, unguided exposures.

This 4-element rare-earth glass system is engineered for a wide 400-700 nm wavelength range, delivering images free of false color, coma, and field curvature. With StarBright XLT coatings, light transmission is maximized, ensuring faint galactic dust lanes and nebulosity are recorded with exceptional contrast and clarity.

A 43.3mm Image Circle for Full-Frame Sensors

Designed for modern astronomy cameras, the RASA 11 V2 produces a 43.3mm optimized image circle, providing vignette-free results on full-frame (35mm format) CMOS and CCD sensors. The usable field extends to 52mm with only minimal performance loss, accommodating even the largest chips available to amateurs. This wide, flat field ensures stars remain sharp across the entire frame, a critical attribute for creating large-scale mosaics or surveying the sky.

• RMS Spot Size: At less than 4.4 μm across the field of view, the optical system resolves finer detail than the pixel size of most modern cameras.
• Off-Axis Illumination: The field is evenly illuminated, maintaining 83% brightness even at 21mm off-axis, simplifying flat-field calibration.
• Central Obstruction: The 114mm central obstruction, at 41% of the aperture diameter, is a necessary trade-off for the extreme f/2.2 speed and wide, corrected field.

Ultra-Stable Focus System (USFS): Eliminating Image Shift

A common challenge in moving-mirror telescopes is image shift and mirror flop. The RASA 11 V2 solves this with the Ultra-Stable Focus System (USFS). By using a precision linear ball bearing to support the primary mirror, the USFS prevents unwanted lateral movement during focusing and maintains focus as the telescope moves across the sky. This robust system is compatible with the optional Celestron Focus Motor for automated and remote focusing routines.

An integrated 12V DC MagLev fan accelerates thermal stabilization, reducing cooldown time so you can start imaging sooner. The fan pulls air through filtered vents, providing optimal airflow without introducing dust into the optical tube.

Imaging Ready with 55mm Back Focus and Dual Dovetails

Every component of the RASA 11 V2 is engineered for seamless integration into your imaging setup. It provides a standard 55mm back focus distance when using the included 42mm T-thread or 48mm camera adapters, matching the requirement of most DSLRs and dedicated astronomy cameras. This simplifies the process of achieving perfect spacing for optimal optical performance.

The optical tube is equipped with two dovetail bars. The primary CGE dovetail bar provides a secure connection to your equatorial mount, while a second CGE bar on top serves as a sturdy mounting point for accessories like a guidescope, power distribution box, or mini-computer.

RASA 11 V2 vs. an 11" SCT with HyperStar: A Dedicated Imaging System

Imagers often compare the RASA 11 to an 11" SCT equipped with a HyperStar lens. While both achieve a similar f-ratio, they are designed for different purposes.

• Competitor Advantage: An SCT with HyperStar offers convertibility. You can remove the HyperStar and use the telescope at its native f/10 for visual observation or high-resolution planetary imaging.
• RASA Advantage: The RASA 11 is a dedicated astrograph, optimized from the ground up for one purpose: wide-field f/2.2 imaging. Its Ultra-Stable Focus System (USFS) provides superior focus stability compared to a standard SCT's moving-mirror focuser. The 4-element lens group is permanently integrated and aligned, removing the complexities of installing and collimating a separate lens assembly.