The C2 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 cameras usually require computer for operation control, image download, processing and storage etc. To operate the camera, you need a computer which:

1. Is compatible with a PC standard and runs modern 32 or 64-bit Windows operating system.

2. Is an x86 or ARM based computer and runs 32 or 64-bit Linux operating system.

   Remark:

   Drivers for 32-bit and 64-bit Linux systems are provided, but the SIPS camera control and image processing software, supplied with the camera, requires Windows operating system.

3. Support for x64 based Apple Macintosh computers is also included.

   Remark:

   Only certain software packages are currently supported on Mac.

C2 cameras are designed to be connected with the host PC through USB 3.0 interface, operating at 5 Gbps. Cameras are also compatible with USB 2.0 port to communicate with a host PC.

Alternatively, it is possible to use the Moravian Camera Ethernet Adapter device. This device can connect up to four Cx (with CMOS sensors) or Gx (with CCD sensors) cameras of any type and offers 1 Gbps and 10/100 Mbps Ethernet interface for direct connection to the host PC. Because the PC then uses TCP/IP protocol to communicate with the cameras, it is possible to insert WiFi adapter or other networking device to the communication path.

The C2 cameras need an external 12 V DC power supply to operate. The wall adapter providing proper voltage is shipped with every camera.

Note the camera must be connected to some optical system (e.g. the telescope) to capture images. The camera is capable of long exposures, necessary to acquire the light from faint objects. If you plan to use the camera with the telescope, make sure the whole telescope/mount setup is capable to track the target object smoothly during long exposures.

C2 Camera Overview

C2 camera head is designed to be easily used with a set of accessories to fulfill various observing needs. Camera head itself is manufactured in two different variants:

• Camera with Internal filter wheel.

• Camera with control port for External filter wheel. This model allows attachment of several variants of external filter wheels with various number of filter positions and sizes.

C2 camera model with Internal filter wheel accepts two sizes of filters:

• Filter wheel with 5 positions for unmounted D31 mm filters or filters in 1.25” threaded cells.

• Filter wheel with 6 positions for unmounted D27 mm (or 1”) filters.

There are two sizes of the External filter wheels, each capable to accept multiple sizes of filters, available for the C2 cameras:

• Extra small “XS” size wheel for 8 unmounted filters D31 mm or filters in 1.25” threaded cells.

• Extra small “XS” size wheel for 7 unmounted filters D36 mm.

• Small “S” size wheel for 12 unmounted filters D31 mm or filters in 1.25” threaded cells.

• Small “S” size wheel for 10 unmounted filters D36 mm.

• Small “S” size wheel for 7 unmounted D50 mm or 2" filter or filters in 2” threaded cells.

Components of C2 Camera system include:

1. C2 camera head with Internal Filter Wheel (5 or 6 positions)

2. C2 camera head capable to control External Filter Wheel

3. External Filter Wheel “XS” size (7 or 8 positions)

4. External Filter Wheel “S” size (10 or 12 positions)

5. C1 guider camera

   Remark:

   C1 cameras are completely independent devices with their own USB connection to the host PC. They can be used either on C2 OAG or on standalone guiding telescope.

   C1 cameras can share the Moravian Camera Ethernet Adapter with up to 3 other Cx cameras to be accessed over TCP/IP network.

6. Off-Axis Guider with M48 × 0.75 thread

7. Off-Axis Guider with M42 × 0.75 thread (T2)

8. Thick adapter base, compensating EFW thickness to achieve proper back focal distance for cameras without filter wheel

9. 1.75” dovetail rail for C2 camera head

10. Camera Ethernet Adapter (x86 CPU)

11. Camera Ethernet Adapter (ARM CPU)

    Remark:

    Moravian Camera Ethernet Adapter allows connection of up to 4 Cx cameras of any type on the one side and 1 Gbps Ethernet on the other side. This adapter allows access to connected Cx cameras using routable TCP/IP protocol over unlimited distance.

12. 5-positions internal filter wheel for 1.25”/D31 mm filters

13. 6-positions internal filter wheel for 1”/D27 mm filters

14. 8-positions external filter wheel “XS” for 1.25”/D31 mm filters

15. 7-positions external filter wheel “XS” for D36 mm filters

16. 12-positions external filter wheel “S” for 1.25”/D31 mm filters

17. 10-positions external filter wheel “S” for D36 mm filters

18. 7-positions external filter wheel “S” for 2”/D50 mm filters

19. M42 × 0.75 (T-thread) or M48 × 0.75 threaded adapters, 55 mm BFD

    Remark:

    Other standard adapters are available, for instance threaded 2" barrel adapter etc.

20. Canon EOS bayonet lens adapter

21. Nikon bayonet lens adapter

C2 Camera Models

C2 camera models are equipped with Sony IMX global shutter CMOS detectors with 3.45 × 3.45 μm or 4.50 × 4.50 μm square pixels. Individual models differ in resolution only.

All used sensors utilize global electronic shutter. This means every pixel within the image is exposed in the same time, as opposed to rolling shutter sensors, which exposes individual lines one after another. There is no difference for long exposures of static objects, but imaging of moving objects using short exposure time using rolling shutter leads to image shape distortions.

Three lines of C2 cameras are available depending on the available dynamic range (bit-depth of the digitized pixels) and pixel size:

• C2 cameras with Sony IMX sensors with 3.45 × 3.45 μm pixels, supporting 8- and 12-bit digitization. Because every 12-bit pixel occupies two bytes when transferred to host PC, 12-bit image download time is longer compared to 8-bit image. Maximal FPS in 8-bit mode is then significantly higher.

• C2 cameras with Sony IMX sensors with 3.45 × 3.45 μm pixels, supporting 12-bit digitization only. As the 12-bit read mode is always used for long-exposure applications (astronomical photography, scientific research) either way, lower theoretical download time in 8-bit mode brings no limitations for real-world scenarios. All other parameters being same (sensor size, resolution, pixels size, noise, …), lower price of these cameras may be then very attractive.

• C2 cameras with Sony IMX sensors with 4.50 × 4.50 μm pixels and 12-bit digitization only. Greater pixels mean higher dynamic range (more electrons can be stored in each pixel before it saturates), but also higher read noise. Still the theoretical S/N is almost the same because of higher signal camera can accumulate. This camera is more suitable for longer focal length telescopes, where small pixels provide oversampled images, and also for research applications, where dynamic range is important.

C2 camera models with 3.45 × 3.45 μm pixels and 8- and 12-bit digitization:

C2 camera models with 3.45 × 3.45 μm pixels and 12-bit digitization only:

C2 camera models with 4.50 × 4.50 μm pixels and 12-bit digitization only:

CMOS Sensors and Camera Electronics

CMOS camera electronics primary role, beside the sensor initialization and some auxiliary functions, is to transfer data from the CMOS detector to the host PC for storage and processing. So, as opposite to CCD cameras, CMOS camera design cannot influence number of important camera features, like the dynamic range (bit-depth of the digitized pixels).

Sensor linearity

The sensors used in C2 cameras shows very good linearity in response to light. This means the camera can be used also for entry-level research projects, like for instance photometry or variable stars etc.

Download speed

As already noted, there are two lines of C2 camera series, differing in the used sensor. The first series with 3.45 × 3.45 μm pixels offers four different read modes:

• 8-bit slow mode with ~132 MPx/s digitization speed

• 12-bit slow mode with ~72 MPx/s digitization speed

• 8-bit fast mode with ~263 MPx/s digitization speed

• 12-bit fast mode with ~132 MPx/s digitization speed

The “A” version of C2 cameras with 3.45 × 3.45 μm pixels offers only single read mode:

• 12-bit fast mode with ~132 MPx/s digitization speed

And the “A” version of C2 cameras with 4.50 × 4.50 μm pixels offers also only one read mode:

• 12-bit fast mode with ~151 MPx/s digitization speed

The digitization speeds mentioned above are valid for USB 3.0 connection. Also please note the digitization speeds do not necessarily lead to corresponding FPS, because every image downloaded has to be processed and displayed, which also consumes time. This time is negligible, if slow-scan camera needs many seconds for image download, but in the case of fast CMOS cameras, time for image processing in the PC (e.g. calculation of image standard deviation etc.) can be longer than image download itself.

Camera gain

Sensors used in C2 cameras offer programmable gain from 0 to 24 dB, which translates to the output signal multiplication from 1× to 15.9×. Gain can be set with 0.1 dB step.

Conversion factors and read noise

Generally, many sensor characteristics depend on the used gain. Hence, we provide two lists of parameters for both minimal and maximal gain.

Camera/sensor parameters for sensors with 3.45 × 3.45 μm pixels:

Camera/sensor parameters for sensors with 4.50 × 4.50 μm pixels:

Exposure control

C2 cameras are capable of very short exposures. The shortest exposure time is 125 μs (1/8000 of second). This is also the step, by which the exposure time is expressed. So, the second shortest exposure is 250 μs etc.

Long exposure timing is controlled by the host PC and there is no upper limit on exposure time. In reality the longest exposures are limited by saturation of the sensor either by incoming light or by dark current (see the following sub-chapter).

Cooling and power supply

Regulated thermoelectric cooling is capable to cool the CMOS sensor up to 45 °C below ambient temperature. The Peltier hot side is cooled by fan. The sensor temperature is regulated with +/-0.1 °C precision. High temperature drop and precision regulation ensure very low dark current for 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 package. The second one measures the temperature inside the camera shell.

The cooling performance slightly depends on the amount of heat generated by a sensor used in the camera:

• In general, lower resolution sensors generate less heat and thus reaches lower temperature.

• The “A” version cameras, using sensors with limited read modes, also generate less heat and reaches lower temperature.

The cooling performance also depends on the environmental conditions and also on the power supply. If the power supply voltage drops below 12 V, the maximum temperature drop is lower.

Power supply

The 12 V DC power supply enables camera operation from arbitrary power source including batteries, wall adapters etc. Universal 100-240 V AC/50-60 Hz, 60 W “brick” adapter is supplied with the camera. Although the camera power consumption does not exceed 40 W, the 60 W power supply ensures noise-free operation.

Mechanical Specifications

Compact and robust camera head measures only 114 × 114 × 65 mm (approx. 4.5 × 4.5 × 2.6 inches). The head is CNC-machined from high-quality aluminum and black anodized. The head itself contains USB-B (device) connector and 12 V DC power plug. Integrated mechanical shutter allows streak-free image readout, as well as automatic dark frame exposures, which are necessary for unattended, robotic setups.

Camera head with integrated Internal filter wheel is 77.5 mm thick. Filter wheel offers 5 positions for standard 1.25-inch threaded filter cells. A variant of filter wheel with 6 positions for unmounted D26 mm filters is also available.

Mechanical shutter

C2 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 acquire dark frames, necessary for proper image calibration.

Mechanical shutter in the C2 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.

Camera with Internal Filter Wheel

Camera with “XS” External Filter Wheel

The “S” sized External filter wheel diameter is greater (viz. External Filter Wheels), but the back focal distance of all external filter wheels is identical.

Camera without filter wheel

If the camera model, intended for usage with External filter wheel, is used without filter wheel at all, two types of adjustable adapter bases can be used.

When a “thin” adapter base, intended for camera with Internal filter wheel, is used, the back focal distance is only 21 mm.

“Thick” adapter base has the same thickness like the External filter wheel. This means all adapters, attached to this thick base, keep the same back focal distance like if attached directly to External filter wheel shell or to a camera with Internal filter wheel and “thin” adapter base.

Optional accessories

Various accessories are offered with C2 cameras to enhance functionality and help camera integration into imaging setups.

External filter wheels

When there is no filter wheel inside the camera head, all electronics and firmware, intended to control it, stays idle. These components can be utilized to control external filter wheel with only little changes. Also the camera front shell can be manufactured thinner, the space for filter wheel is superfluous.

Telescope adapters

Various telescope and lens adapters for the C2 cameras are offered. Users can choose any adapter according to their needs and other adapters can be ordered separately.

• 2-inch barrel — adapter for standard 2" focusers.

• T-thread short — M42 × 0.75 inner thread adapter.

• T-thread with 55 mm BFD — M42 × 0.75 inner thread adapter, preserves 55 mm back focal distance.

• M48 × 0.75 short — adapter with inner thread M48 × 0.75.

• M48 × 0.75with 55 mm BFD — adapter with inner thread M48 × 0.75, preserves 55 mm back focal distance.

• Canon EOS bayonet — standard Canon EOS lens adapter, preserves 44 mm back focal distance.

• Nikon F bayonet — standard Nikon F lens adapter, preserves 46.5 mm back focal distance.

All telescope/lens adapters of the C2 series of cameras can be slightly tilted. This feature is introduced to compensate for possible misalignments in perpendicularity of the telescope optical axis and sensor plane.

The C2 camera telescope adapters are attached using three “pulling” screws. As the adapter tilt is adjustable, another three “pushing” screws are intended to fix the adapter after some pulling screw is released to adjust the tilt.

Adjustable telescope/lens adapters are attached slightly differently depending if the adapter is attached directly to the camera head (e.g. when camera is equipped with internal filter wheel) or to the External filter wheel case.

• C2 adapters are not mounted directly on the camera head. Instead a tilting adapter base, holding the circular spring, is always used.

• If the External filter wheel is used, the adapted base is not necessary, as the External filter wheel front plate is already designed to hold the spring and it also contains threads to fix respective adapters.

Off-Axis Guider Adapter (OAG)

C2 camera can be optionally equipped with Off-Axis Guider Adapter. This adapter contains flat mirror, tilted by 45° to the optical axis. This mirror reflects part of the incoming light into guider camera port. The mirror is located far enough from the optical axis not to block light coming to the main camera sensor, so the optics must be capable to create large enough field of view to illuminate the tilted mirror.

C2-OAG is manufactured in two variants, one with M42 × 0.75 thread (T-thread) and another with M48 × 0.75 thread. Both variants are designed to be compatible with external filter wheels and to preserve 55 mm distance from the sensor.

If the OAG has to be used on camera with internal filter wheel, the OAG is mounted to adapter base like any other adapter. Resulting Back focal distance remains the same.

OAG guider port is compatible with C1 cameras (and also older G0 and G1). It is necessary to replace the CS/1.25” adapter with short, 10 mm variant in the case of C1 cameras. Because C1 cameras follow CS-mount standard, (BFD 12.5 mm), any camera following this standard with 10 mm long 1.25” adapter should work properly with the C2-OAG.

Attaching camera head to the telescope mount

C2 camera heads are equipped with “tripod” thread (0.25”) as well as four M4 threaded holes on the top side of the camera head.

This thread can be used to attach 1.75 inch “dovetail bar” (Vixen standard). It is then possible to attach the camera head, e.g. equipped with photographic lens, directly to various telescope mounts supporting this standard.

Tool-less desiccant containers

C2 cameras employ the same desiccant container like the larger C3 and C4 cameras, aw well as CCD based G2, G3 and G4 cameras. The whole container can be unscrewed, so it is possible to exchange silica-gel without the necessity to remove the camera from the telescope.

Container shipped with the camera by default does not exceed the camera head outline. It is equipped with a slot for tool (a plastic tool is included with every camera, but e.g. some coin can be used, too), allowing releasing and also tightening of the container.

This design also allows usage of some optional parts:

• Threaded hermetic cap, allowing sealing of the dried container when it is not immediately attached to the camera head.

• Alternate (somewhat longer) desiccant container, modified to be able to be screw in and tightened (as well as released and screwed out) without any tool.

Camera head color variants

Camera head is available in several color variants of the center plate. Visit manufacturer's web pages for current offering.

Moravian Camera Ethernet Adapter

The Moravian Camera Ethernet Adapter device allows connection of up to four Cx cameras of any type on one side and 1 Gbps Ethernet interface on the other side. So, this device allows attaching of cameras to virtually unlimited distance using the routable TCP/IP protocol.

Moravian Camera Ethernet Adapter device is described in detail here.

Software support

Software and driver support of the Cx series CMOS cameras is as rich as is the case of their Gx series CCD camera siblings.

However, latest versions of all software packages and drivers has to be installed to use Cx cameras.

• If the C2 camera is connected directly to host PC using USB cable, a new system driver CxCamera.sys must be installed (see the “Installing and Using Drivers and Software” manual, shipped with every camera). The system driver pre-installation package version 2.3 and later contains this driver.

• When the C2 camera is connected through the Moravian Camera Ethernet Adapter device, the device should be updated to firmware version 42 or later to work with CMOS cameras (see the “Moravian Camera Ethernet Adapter User's Guide” for firmware update procedure).

  Hint:

  When the SIPS is connected to the camera using the Moravian Camera Ethernet Adapter device, it shows the attached device firmware version in the Windows Action Center notification area.

• Linux driver packages and libraries must be upgraded to latest versions, too. See the Download section of this site for details.

The SIPS (Scientific Image Processing System) software package version 3.21 or later is necessary to control C2 cameras including latest C2-7000.

C2 camera drivers for 3^rd party software packages also need to be updated to work with C2 cameras. Minimum versions for respective drivers are:

• ASCOM drivers version 5.1

• Drivers for TheSkyX (all versions for Windows, MacOS and Linux) version 2.2

• Astroart drivers version 3.2

SIPS

Powerful SIPS (Scientific Image Processing System) software, supplied with the camera, allows complete camera control (exposures, cooling, filter selection etc.). Also automatic sequences of images with different filters, different binning etc. are supported. With full ASCOM standard support, SIPS can be also used to control other observatory equipment. Specifically the telescope mounts, but also other devices (focusers, dome or roof controllers, GPS receivers etc.).

SIPS also supports automatic guiding, including image dithering. Both “autoguider” port hardware interface (6-wire cable) and mount “Pulse-Guide API” guiding methods are supported. For hi-quality mounts, capable to track without the necessity to guide at last during one exposure, inter-image guiding using the main camera only is available.

But SIPS is capable to do much more than just camera and observatory control. Many tools for image calibration, 16 and 32 bit FITS file handling, image set processing (e.g. median combine), image transformation, image export etc. are available.

As the first “S” in the abbreviation SIPS means Scientific, the software supports astrometric image reduction as well as photometric processing of image series.

SIPS software package is freely available for download from this www site. All functions are thoroughly described in the SIPS User's Manual, installed with every copy of the software.

Drivers for ASCOM standard as well as native drivers for third-party software are also available (e.g. TheSkyX, AstroArt, etc.). Visit the download page of this web site for current list of available drivers, please.

Also INDI drivers for 32 bit and 64 bit Linux running on x86 and ARM are available. Also drivers for TheSkyX package running on macOS are supplied with the camera.

Automatic guiding

SIPS software package allows automatic guiding of the astronomical telescope mounts using separate guiding camera. Proper and reliable automatic guiding utilizing the computational power of Personal Computer (e.g. calculation of star centroid allows guiding with sub-pixel precision) is not simple task. Guiding complexity corresponds to number of parameters, which must be entered (or automatically measured).

The “Guiding” tool allows switching of autoguiding on and off, starting of the automatic calibration procedure and recalculation of autoguiding parameters when the telescope changes declination without the necessity of new calibration. Also swapping of the German Equatorial mount no longer requires new autoguider calibration. There is also a graph showing time history of guide star offsets from reference position in both axes. The length of graph history as well as the graph range can be freely defined, so the graph can be adjusted according to particular mount errors and periodic error period length. Complete log of calibration procedure, detected offsets, correction pulses etc. is also shown in this tool. The log can by anytime saved to log file.

An alternative to classic autoguiding is the inter-image guiding, designed for modern mounts, which are precise enough to keep tracking with sub-pixel precision through the single exposure, and irregularities only appear on the multiple-exposure time-span. Inter-image guiding then performs slight mount position fixes between individual exposures of the main camera, which eliminates “traveling” of the observed objects through the detector area during observing session. This guiding method uses main imaging camera, it does not use another guiding camera and naturally does not need neither OAG nor separate guiding telescope to feed the light into it.

Advanced reconstruction of color information of single-shot-color cameras

Color sensors have red, green and blue filters applied directly on individual pixels (so-called Bayer mask).

Every pixel registers light of particular color only (red, green or blue). But color image should contain all three colors for every pixel. So it is necessary to calculate missing information from values of neighboring pixels.

There are many ways how to calculate missing color values — from simple extending of colors to neighboring pixels (this method leads to coarse images with visible color errors) to methods based on bi-linear or bi-cubic interpolation to even more advanced multi-pass methods etc.

Bi-linear interpolation provides significantly better results than simple extending of color information to neighboring pixels and still it is fast enough. But if the telescope/lens resolution is close to the size of individual pixels, color artifacts appear close to fine details, as demonstrated by the image below left.

Multi-pass algorithm is significantly slower compared to single-pass bi-linear interpolation, but the resulting image is much better, especially in fine details. This method allows using of color camera resolution to its limits.

SIPS offers choosing of color image interpolation method in both “Image Transform” and “New Image Transform” tools. For fast image previews or if the smallest details are significantly bigger than is the pixel size (be it due to seeing or resolution of the used telescope/lens) the fast bi-linear interpolation is good enough. But the best results can be achieved using multi-pass method.

Shipping and Packaging

C2 cameras are supplied in the foam-filled, hard carrying case containing:

• Camera body with a user-chosen telescope adapter. If ordered, the filter wheel is already mounted inside the camera head and filters are threaded into place (if ordered).

• A 100-240 V AC input, 12 V DC output “brick” adapter with 1.8 m long power cable.

• 2 m long USB 3.0 A-B cable for connecting camera to host PC.

• USB Flash Drive with camera drivers, SIPS software package with electronic documentation and PDF version of User's Manual.

• A printed copy of camera User's Manual

Image Gallery

Example images captured with C2 cameras.

All images published with permission of their respective authors.