QHYCCD QHY268C Color

Sony IMX571: A 26MP, APS-C Format Back-Illuminated Sensor

The core of the QHY268C is its 26MP Sony IMX571 sensor, which provides a large field of view and high resolution from its 6252 x 4176 pixel array. The back-illuminated (BSI) architecture improves quantum efficiency by placing the sensor's wiring below the photosensitive layer, allowing more light to reach the pixels for increased sensitivity. The APS-C format gives a wide field for large deep-sky objects.

The 3.76µm pixels give fine sampling on short and medium focal lengths; on long focal lengths, binning can be used to match the seeing.

Multiple Readout Modes: From 1.1e- Noise to 80ke- Full Well

The QHY268C features several user-selectable readout modes, allowing you to tailor the camera's performance to your specific target. This flexibility is key to optimizing dynamic range and signal-to-noise ratio under different conditions.

• High Gain Mode: For faint, low-contrast targets like distant galaxies or molecular clouds, use this mode when you have to capture at high gain; for the best results, set gain 56, the HGC/LGC switch point.
• Extended Full Well Mode: When imaging bright objects with extreme dynamic range, such as the Orion Nebula (M42) or dense star clusters, this mode expands the pixel capacity to 80ke-. This prevents bright stars from saturating, preserving their color and the faint nebulosity surrounding them.
• Photographic Mode: This standard mode offers a balanced profile suitable for most general deep-sky imaging, providing low read noise and a generous full well capacity of 51ke-.

True 16-Bit A/D with Zero Amplifier Glow

The QHY268C employs a true, native 16-bit Analog-to-Digital converter directly on the sensor. This system samples the incoming signal at 65,536 distinct levels, giving smooth tonal gradations in bright areas without posterization.

The QHY268C has zero amplifier glow, so long exposures do not show the edge brightening that readout electronics can cause. Raw frames are more uniform, which keeps calibration simple.

-35°C Cooling and 0.0005 e-/sec Dark Current

Long-exposure deep-sky astrophotography demands aggressive thermal control to minimize noise. The QHY268C integrates a powerful dual-stage thermoelectric (TEC) cooler that achieves a typical thermal depression of -35°C below the ambient temperature. This robust cooling drastically reduces thermal noise, or dark current, to just 0.0005 electrons per pixel per second when the sensor is held at -20°C.

On humid nights the integrated anti-dew heater on the optical window prevents frost and condensation. The sensor chamber is kept dry by QHYCCD's silicon gel tube socket design, and the included desiccant tube can be connected if moisture ever appears inside.

1GB DDR3 Buffer for 6.8 FPS Uninterrupted Transfer

To ensure smooth and reliable data transfer, the QHY268C includes a 1GB DDR3 memory buffer. This internal cache helps prevent dropped frames when the computer is busy. The buffer holds the data from the sensor before transmitting it over the USB 3.0 interface, ensuring the integrity of every frame.

At its full 26MP resolution, the camera captures 6.8 frames per second in 8-bit mode. You can define a smaller Region of Interest (ROI). With a 480-line ROI the frame rate rises to 50 FPS (8-bit), which helps with focusing and fast captures of bright targets.

Optical Train Integration: 14.5mm Back Focus and M54 Threads

The QHY268C is designed for straightforward integration into complex optical trains. It features a short back focus distance of 14.5mm (±0.2mm), which provides more space for a filter wheel drawer, an electric CAA or a DSLR lens. Since 2023 the QHY268C uses the shorter top part of the QHY268M; earlier QHY268C cameras had 17.5mm plus the 6mm CAA.

The telescope interface is M54 or M48, combined with adapters. The included adapter kit and the M54 to 2" nosepiece let you thread the camera into an imaging train or slide it into a 2" focuser.

QHY268C vs. QHY268M: One-Shot Color vs. Monochrome

The QHY268 series is available in both color (QHY268C) and monochrome (QHY268M) versions, each serving a different imaging workflow. The choice depends on your workflow.

The QHY268C (Color) uses a Bayer matrix over the sensor to capture red, green, and blue data in a single exposure. This "One-Shot Color" (OSC) approach needs no filter wheel and gives a full-color image from each exposure.

The QHY268M (Monochrome) version lacks the Bayer matrix, making it inherently more sensitive as all pixels collect all incoming light. It requires separate exposures through red, green, and blue filters to create a color image. While this process is more time-consuming, it yields higher-resolution images and is essential for advanced narrowband imaging (H-alpha, OIII, SII). The monochrome version also includes an internal humidity sensor, a feature not present in the QHY268C.