SBIG Aluma AC4040 Mono

An Advanced sCMOS Camera for Research and Deep Sky

The Aluma AC4040 is designed as an advanced scientific CMOS instrument for astronomical imaging systems. It bridges the gap between traditional CCD performance and modern sCMOS advantages, offering the large format and pixel size favored for research applications alongside the low noise and high frame rates characteristic of CMOS technology. This makes it suited to observatories, advanced amateur astronomers, and specialized applications like space situational awareness.

Whether you are hunting for faint galactic structure, or tracking orbital debris, the AC4040 provides the core capabilities for high-fidelity data acquisition. Its architecture is built for robotic and remote operation, featuring both electronic and mechanical shutters for automated dark frame subtraction and precise exposure control from 0.001 to 3600 seconds.

The 16.8 MP, 52mm Diagonal GSENSE4040 Sensor

At the heart of the Aluma AC4040 is the Gpixel GSENSE4040, a scientific CMOS sensor with a 4096 x 4096 pixel array. The sensor measures 36.8 mm on each side, creating a square format with a 52.0 mm diagonal well-suited to the corrected image circles of large astrographs and Ritchey-Chrétien telescopes. Each pixel is 9 µm square, providing a balance of resolution and light-gathering capacity for a wide range of focal lengths.

The camera is available in two primary sensor configurations to match specific scientific goals. The standard Front-Side Illuminated (FSI) model offers a peak QE of 74% with lower dark current, making it the best choice for most long-exposure deep-sky applications. For specialized research, a Back-Side Illuminated (BSI) version is available, boosting peak QE to 95% and extending sensitivity into the UV spectrum.

• FSI Sensor: Peak QE of 74%. Recommended for general astronomical imaging due to its excellent balance of sensitivity, lower dark current, and dynamic range. Available in Class 1 or economical Class 2 grades.
• BSI Sensor: Peak QE of 95%. Offers significant UV sensitivity beyond 250 nm, and is best suited to applications that need UV sensitivity or rapid acquisition of faint targets, such as Space Situational Awareness. The trade-off is much higher dark current and lower full-well capacity than the FSI sensor.
• Protective Window Options: BSI models can be ordered with standard VIS-NIR coatings or optional UV-VIS coatings to optimize performance for ultraviolet research.

StackPro™ and HDR Mode: Maximizing Dynamic Range

To overcome the dynamic range limitations inherent in some CMOS sensors compared to their CCD counterparts, the Aluma AC4040 features two advanced acquisition modes. These techniques leverage the sensor's low read noise to build images with greater dynamic range without overwhelming data storage.

The StackPro™ feature performs image stacking directly inside the camera. It can automatically subdivide a long exposure into as many as 16 shorter sub-exposures, stacking them in the camera's hardware before download. This emulates the behavior of a long CCD exposure, reduces on-sensor logic glow, and saves significant disk space and post-processing time. Additionally, the GSENSE4040 sensor supports a native High Dynamic Range (HDR) mode, where high-gain and low-gain readouts are captured simultaneously to preserve detail in both faint and bright regions of an object.

A Regulated 35°C Delta: Thermoelectric and Liquid Cooling

Effective thermal management is critical for minimizing noise in long exposures. The Aluma AC4040 uses a powerful two-stage thermoelectric cooler (TEC) coupled with a proven pin heatsink design to achieve a regulated cooling delta of 35 °C below ambient temperature. SBIG's SmartCooling™ technology intelligently manages the TEC and fan operation to maintain a stable sensor temperature, which is essential for accurate calibration with dark and bias frames.

For observatories operating in high ambient temperatures or demanding maximum thermal stability, the camera body includes integrated ports for an optional liquid cooling system. This improves cooling efficiency and further minimizes dark current for the most sensitive applications. The camera also features a user-rechargeable desiccant plug, allowing you to maintain a dry, frost-free sensor chamber without requiring factory service.

Dual Shutters and 0.75s Download Speeds

The Aluma AC4040 provides two shutter systems for maximum flexibility. The GSENSE4040 sensor has an electronic rolling shutter for precise exposure timing, while an integrated mechanical shutter allows for effortless and automated dark frame acquisition. This dual system is a key feature for robotic observatories, eliminating the need to manually cover the telescope to capture calibration frames.

Despite the large 16.8 megapixel resolution, the camera's advanced design and USB 3.0 interface enable a full-frame download in just 0.75 seconds. This high-speed readout minimizes the dead time between exposures, increasing observational efficiency during valuable clear-sky hours.

USB 3.0, 12V Power, and MaxIm LT Software

The camera connects to a control computer via a high-speed USB 3.0 port, which is also backward-compatible with USB 2.0 for use with longer cable runs. Power is supplied by a standard 12V DC source capable of 8A, making it suitable for both permanent observatory installations and field setups with appropriate power tanks. An I2C auxiliary port is also included for controlling compatible SBIG filter wheels.

Every Aluma AC4040 includes a license for MaxIm LT software for Windows. This powerful software provides comprehensive control over the camera, filter wheel, and an autoguider. It also includes advanced image processing tools, with an available upgrade path to MaxIm DL Pro for full observatory integration and analysis capabilities. Standard drivers are provided for Windows 11 and Linux Ubuntu 22.04 LTS.

Mechanical Design: 21.7mm Back Focus and a 1600g Platform

Weighing 1600 g (3.5 lbs), the Aluma AC4040 is a substantial camera built for large, stable imaging platforms. The front of the camera features the standard SBIG 3-inch mounting plate with a large-format 6-32 UNC bolt pattern for direct, rigid connection to compatible accessories. The sensor is positioned to provide a 21.7 mm back focus distance from the front mounting face, a critical dimension for planning your imaging train with correctors, filter wheels, and off-axis guiders.

Integrated Guiding with the StarChaser SC-4

For precise tracking during long exposures, the Aluma AC4040 is designed to integrate seamlessly with the SBIG StarChaser SC-4. This off-axis guider (OAG) bolts directly to the front of the Aluma AC camera body, providing a solid platform for autoguiding. By using an OAG, you guide with the main telescope's optics, eliminating differential flexure that can plague separate guidescopes and result in elongated stars.

Adaptive Optics and Filter Wheel Ecosystem

The Aluma AC4040 serves as the core of a fully integrated, research-grade imaging system. It is compatible with SBIG's AO-X adaptive optics unit, which uses a high-speed tip-tilt window to make fine corrections to the image position, actively reducing the effects of atmospheric seeing and mount errors. The AO-X requires the use of the StarChaser SC-4 guider for operation with the Aluma AC series.

• Filter Wheel Compatibility: The AC4040 supports large-format filters, essential for covering its 52.0 mm diagonal sensor without vignetting. It is compatible with the 10-position SBIG AFW-10-50SQ for 50mm square filters and the 7-position FW7-STX wheel.
• Adaptive Optics: The SBIG AO-X provides real-time seeing correction, delivering sharper stars and finer detail than guiding alone can achieve.

Applications in Scientific Imaging and Space Domain Awareness

Beyond deep-sky imaging, the Aluma AC4040 is a research-grade scientific camera. Its combination of a large sensor, high sensitivity, and fast readout makes it a powerful tool for scientific imaging and space domain awareness (SDA).

The BSI version, with its UV sensitivity beyond 250 nm, is best suited to applications where UV sensitivity is required. For SDA applications, the camera's ability to rapidly acquire images of faint targets across a wide field of view is critical for detecting and tracking satellites, asteroids, and other orbital objects.

Aluma AC4040 vs. STX-16803: A Generational Leap in Sensitivity

Compared to SBIG's previous flagship CCD camera, the STX-16803, the Aluma AC4040 represents a significant advancement in imaging technology. The primary advantage lies in the quantum efficiency of the new sCMOS sensor.

The STX-16803's venerable KAF-16803 CCD had a respectable peak QE of 60%. The standard FSI sensor in the Aluma AC4040 improves upon this with a peak QE of 74%. More importantly, the QE curve is much broader, maintaining high sensitivity across the entire visible spectrum from 450 nm to over 900 nm. This results in a dramatic increase in overall signal captured in the same exposure time, making the AC4040 a far more efficient instrument.