The QHY 268M Monochrome contains the Sony IMX571, a high performance back illuminated cooled monochrome sensor with true 16-bit A/D. This translates to a dynamic range of 14 stops for vibrant and natural colours, even in faint or dark nebulae. The pixels have a size of 3.8 µm which is an excellent value for telescopes with different focal lengths.
Differently from the other cameras, QHY developed for the 268M three different capturing modes:
- #0 Photographic Mode: this is the standard mode that can be used for general astrophotography. The readout noise rapidly drops between 25 and 30 (2.5e- at gain 30) which is ideal for long focal length telescopes where a longer exposure time is required. The trade-off at gain 30 is a lower full well capacity at 30,000 e-. In fast telescopes (f/2.2 – f/4) the gain can be set to zero to use the maximum full well capacity (75,000 e-).
- #1 High Gain Mode: the readout noise is much lower at 3e- between gain 0 and 55. This mode is ideal for narrowband imaging where long exposures are generally required.
- #2 Extended Full Well: ideal for objects with bright stars or strong contrasts. The full well capacity is at the highest level along the entire gain range.
The camera has a two-stage TEC cooling system that brings the temperature of the sensor 35C° below ambient for low noise imaging, even in warm climates. The dark current at -20°C is only 0.0005 electron/pixels. In addition to thermoelectric cooling, QHYCCD employs a unique thermal noise control technology to reduce CMOS sensor noise to a very low value without affecting the integrity of the raw image. The QHYCCD proprietary technology produces a much better noise reduction than any other astronomy camera in the market. The QHY 268M employs a full anti-dew technology for both CMOS sensor cover glass and the optical window to avoid condensation or ice crystal in the camera.
The 1GB DDR II memory buffer facilitates the download of images to the computer, especially when USB traffic is high, the writing speed of your computer is slow or occupied with other processes.
In order to avoid halos around bright stars, the QHY 268M has an AR coated optical window on both sides rather than the common IR/UV cut coating. Also, the protection glass of the sensor is AR coated to maximize light transmission and minimize internal reflections.
Every QHY 268M camera is carefully calibrated with a high-precision axis measurement device. Orthogonal placement of the sensor in the camera body is guaranteed to be flat to the image plane with a precision better than +/-20µm across the sensor, from edge to edge, so there is no need to adjust the camera tilt. This is an enormous advantage especially in fast telescopes such as F/2.8-F/4 astrographs which are very sensitive to tilted sensors.
The QHY 268M has zero amplifier glow no matter how long the exposure is.
The differences between the Photographic and Professional versions include:
- Professional version has a high-speed fiber interface and USB3.0 interface. Photographic version has only a USB3.0 interface.
- Professional version may has more on-camera DDR3 memory than the Photographic version.
- Professional version has rich, external, expandable I/O signals as well as a rich resource that allow the user to customize the FPGA inside the camera.
- Professional version is more expensive than Photographic version.
- Professional version has a longer body to accommodate the length of the optical fiber interface.
- Camera Window is AR+AR