Moravian C4-16000C1EC Mono CMOS Camera - Sensor D=52 mm

C4 Series CMOS Cameras

The C4-16000 cooled scientific CMOS camera sensors offer the same geometry like the CCDs in the famous G4-16000 cameras — sensor size 37 × 37 mm, 9 μm pixels and 16 MPx (4k × 4k) resolution. Also the mechanical design of C4 cameras inherits from G4 Mark II cameras, which makes the C4 camera line fully compatible with vast range of telescope adapters, off-axis guider adapters, filter wheels, Camera Ethernet adapters, guiding cameras etc.

Mechanical design of the C4 series of astronomical CMOS cameras inherits from earlier CCD-based G4 Mark II cameras, which makes the C4 camera line fully compatible with vast range of telescope adapters, off-axis guider adapters, filter wheels, Camera Ethernet adapters, guiding cameras etc.
Rich software and driver support allow usage of C4 camera without necessity to invest into any 3rd party software package thanks to included free SIPS software package. However, ASCOM (for Windows) and INDI (for Linux) drivers and Linux driver libraries are shipped with the camera, provide the way to integrate C4 camera with broad variety of camera control programs.
The C4 cameras are designed to work in cooperation with a host Personal Computer (PC). As opposite to digital still cameras, which are operated independently on the computer, the scientific cooled cameras usually require computer for operation control, image download, processing and storage etc.

C4 cameras are designed to be attached to host PC through very fast USB 3.0 port. While C4 cameras remain compatible with older (and slower) USB 2.0 interface, image download time is significantly longer.

The C4 cameras need an external power supply to operate. It is not possible to run the camera from the power lines provided by the USB cable, which is common for simple imagers. C4 cameras integrate highly efficient CMOS sensor cooling, shutter and possibly filter wheel, so their power requirements significantly exceed USB line power capabilities. On the other side separate power source eliminates problems with voltage drop on long USB cables or with drawing of laptop batteries etc.

CMOS Sensor and Camera Electronics
C4 cameras are equipped with Gpixel GSENSE4040 CMOS detectors with resolution 4096 × 4096 pixels. Pixel size is 9 × 9 μm, which leads to almost 37 × 37 mm light sensitive area.
The GSENSE4040 sensor is equipped with 12-bit ADCs (Analog to Digital Converters) only. However, there are two sets of ADCs inside the sensor, each capable to digitize the image with different gain — one set of ADCs uses low-gain channel, while the second set uses high-gain channel. Both 12-bit outputs of each ADC set can be combined to single image with true 16-bit dynamic range (such combined image is often called 16-bit HDR for High Dynamic Range).

Exposure control
C4 cameras are capable of very short exposures, the shortest exposure time is approx. 21 μs. However, the sensor employs so-called “rolling shutter”. This means the exposure does not start over the whole sensor at once, but exposure of subsequent lines begins with 21 μs delay and the whole sensor is illuminated 8.6 ms after exposure starts. Similarly, end of exposure and pixel digitization is performed line by line with the same delay between lines.
There is no practical limit on maximal exposure length, but in reality, the longest exposures are limited by saturation of the sensor either by incoming light or by dark current (see the following chapter about sensor cooling).

Hardware binning
The used GSENSE4040 sensor implements 2 × 2 binning mode in hardware in addition to normal 1 × 1 binning.
However, the back-side illuminated version of this sensor GSENSE4040BSI does not implement any binning mode in hardware. Also, the camera driver and user’s applications offer much wider variety of binning modes up to 3 × 3 and 4 × 4 pixels as well as all combinations of asymmetrical binning modes 1 × 2, 1 × 3, 2 × 4 etc. This is why the camera driver performs all binning combinations in software and does not rely on the limited capabilities of the sensor hardware binning.

Mechanical shutter*
C4 cameras are equipped with mechanical shutter, which is very important feature allowing unattended observations (fully robotic or just remote setups). Without mechanical shutter, it is not possible to automatically acquire dark frames, necessary for proper image calibration etc.
Mechanical shutter in the C4 cameras is designed to be as reliable as possible, number of open/close cycles is virtually unlimited, because there are no surfaces rubbing against each other. The price for high reliability is slow shutter motion. Luckily, mechanical shuttering is not necessary for exposure control, only for taking dark frames and possibly bias frames — all used CMOS sensors are equipped with electronic shuttering.
Camera firmware optimizes the shutter operation to avoid unnecessary movements. If a series of light images is taken immediately one after another, the shutter remains open not to introduce quite significant delay of the close/open cycle between each pair of subsequent light images. In the case next image has to be dark or bias frame, shutter closes prior to dark frame exposure and vice versa — shutter remains closed if a series of dark frames is acquired and opens only prior to next light frame. If no exposure is taken for approximately 1 second while the shutter is open (this means after a light image exposure), camera firmware closes the shutter to cover the sensor from incoming light.

[*Cooling
Regulated thermoelectric cooling is capable to cool the CMOS sensor up to 35 °C below ambient temperature. The Peltier hot side is cooled by a fans. The sensor temperature is regulated with ±0.1 °C precision. Cooling and precision regulation ensure the dark current does not ruin long exposures and allow proper image calibration.
The camera head contains two temperature sensors — the first sensor measures directly the temperature of the CMOS sensor. The second one measures the temperature inside the camera shell.

Note: Some pictures show accessories which are not included in the scope of delivery.