C1 camera models are equipped with Sony IMX global shutter CMOS detectors with 3.45 × 3.45 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.

Two lines of C1 cameras are available depending on the available dynamic range (bit-depth of the digitized pixels):

• C1 cameras with Sony IMX sensors 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.

• C1 cameras with Sony IMX sensors 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.

C1 camera models with 8- and 12-bit digitization:

C1 camera models with 12-bit digitization only:

The C1 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 compatible with a PC standard 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.

C1 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 C1 cameras do not need an external power supply to operate, they are powered through the USB connection from the host PC.

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.

C1 Camera System

Components of the C1 Camera system include:

1. C1 camera head with CS-mount adapter

2. C1 camera head with combined T-thread (M42×0.75) and CS-mount adapter

3. C/CS-mount to 1.25” barrel adapter

4. Short (10 mm) variant of C/CS-mount to 1.25” barrel adapter, intended for usage with OAG

5. Off-Axis Guider adapter (OAG) to large cooled (C2/C3/C4 or G2/G3/G4) camera

   Remark:

   OAG shown here is not exactly part of the C1 camera system. It is intended for C2/G2 cameras and only accommodates C1 camera for guiding.

   To allow the C1 camera to work with OAG, it is necessary to use the CS-mount adapter. C1 camera with T-thread adapter is not compatible with OAG.

   Note the C1 cameras are also compatible with larger OAGs for C3/C4 and G3/G4 cameras, not shown here.

6. Extension tube with M48 × 0.75 thread and 55 mm back focal distance

7. Extension tube with M42 × 0.75 thread and 55 mm back focal distance (standard T-thread adapter)

8. Adapter for Canon EOS bayonet lens

9. Adapter for Nikon bayonet lens

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 C1 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 brighter variable stars etc.

Download speed

As already noted, there are two lines of C1 camera series, differing in the used sensor. The first series 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 C1 cameras offers only single read mode:

• 12-bit fast mode with ~132 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 C1 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.

Exposure control

C1 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).

Sensor Cooling

Dark current is an inherent feature of all silicone circuits. It is called “dark”, because it is generated regardless if the sensor is exposed to light or not. Dark current, injected into individual pixels, appear in image as noise. The longer exposure, the greater amount of noise is present in every image. As it is generated by random movement of particles, it depends on the temperature exponentially (this is why the noise generated by dark current is also denoted “thermal noise”). Typically, lowering the sensor temperature by 6 or 7 °C halves the dark current.

While the C1 cameras are not equipped with active thermo-electric (Peltier) cooling, they are still equipped with a small fan, exchanging the air inside the camera body. What's more, a small heat sink is located directly on the sensor (with the exception of the C1-1500 model, which sensor is too small for heat sink) to remove as much heat as possible. So, the C1 sensor cannot be cooled below the ambient temperature, but its temperature is kept as close to environment as possible. Compared to closed designs, the sensor temperature in the C1 camera can be up to 10°C lower and resulting dark current may be less than half.

The fan operation can be controlled from the software. SIPS directly offers a slider controlling fan in the “Cooling” tab of the main camera control tool window. Camera drivers for other software must rely on driver configuration dialog box to control fan.

Autoguider port

A lot of astronomical telescope mounts (especially the mass-manufactured ones) are not precise enough to keep the star images perfectly round during long exposures without small corrections. Cooled astronomical cameras and digital SLR cameras allow perfectly sharp and high-resolution images, so even a small irregularity in mount tracking appears as star image deformations. C1 cameras were designed especially with automatic mount guiding on mind.

C1 cameras were designed to operate without any mechanically moving parts (with the exception of magnetically levitating fan). Electronic shutter allows extremely short exposures and also obtaining thousands of images in a short time, which is necessary for quality guiding.

C1 cameras work in connection with a host computer (PC). Guiding corrections are not calculated in the camera itself, it only sends acquired images to the PC. The software running on the PC calculates the difference from required state and sends appropriate corrections to the telescope mount. The plus side of using a host PC CPU to process images is the fact, that current PCs provide overwhelming computational power compared to any embedded processor inside the guiding camera. Guiding algorithms then can determine star position with sub-pixel precision, can match multiple stars to calculate average difference, which limits the effects of seeing, etc.

Calculated corrections can be sent back to mount using PC-to-mount link. If the mount controller does not support so-called “Pulse Guide” commands, it is possible to use “Autoguider” port. It is enough to connect the C1 camera and the mount using standard 6-wire cable and guide the mount through the camera.

The maximum sinking current of each pin of the C1 camera is 400 mA. If the mount does not treat the autoguider port as logical input only, but switches the guiding motors directly by these signals, a relay box must be inserted between the camera and the mount. The relay box ensures switching of currents required by the mount.

The Autoguider port follows the de-facto standard introduced by SBIG ST-4 autoguider. The pins have the following functions:

Mechanical Specifications

C1 camera head is designed to be lightweight and compact to be easily attached even to small telescopes or finders. Compact and robust camera head measures only 57 × 57 × 48 mm not including the lens adapter.

The head is CNC-machined from high-quality aluminum and black anodized. The head itself contains USB-B 3.0 (device) connector and standard 6-pin “autoguider” connector.

Telescope/lens adapters

C1 cameras are supplied with two types of telescope/lens adapters:

• Adapter with 1/32 UN thread and 12.5 mm Back Focal Distance (CS-mount).

• Adapter with M42 × 0.75 thread (T-thread) and 18.5 mm Back Focal Distance. This adapter also contains inner thread 1/32 UN with 12.5 mm BFD (CS-mount).

CS-mount it compatible with vast number of CCTV lenses. If C-mount lens has to be used (with 17.5 mm Back Focal Distance), simple 5 mm thick adapter ring can be used.

C-to-1.25” barrel adapter, compatible with standard 1.25” eyepieces, is included into camera package. So, the C1 camera can be easily mounted into virtually every astronomical telescope instead of an eyepiece.

The T-mount interface (also known as T-thread adapter) is defined by thread dimensions M42 × 0.75 as well as by 55 mm Back focal Distance. T-thread adapter for C1 cameras does not comply to the second parameter, its BFD is only 18.5 mm. The 55 mm BFD is not required in all applications and keeping such relatively large BFD would make the adapter quite bulky.

Still, an extension tube with male M42 × 0.75 thread is available. This extension tube converts the C1 camera BFD to 55 mm, required by numerous focal-reducers, field-flatteners, coma-correctors and other optical elements.

There are two variants of the 55 mm BFD extension tubes available:

• Extension tube with M42 × 0.75 (T-thread) on the telescope side.

• Extension tube with larger M48 × 0.75 thread on the telescope side.

Also, extension tubes with bayonet interfaces for standard photographic lenses are available:

• Extension tube with Nikon bayonet adapter.

• Extension tube with Canon EOS bayonet adapter.

Tripod and metric threads

If the C1 camera is not attached to the telescope focuser through its telescope/lens adapter, it can be attached to standard photographic tripod using 0.25” thread. Another possibility is to use 4 metric M3 threaded holes, also located on the bottom side of the camera head.

C1 Camera Dimensions

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 C1 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 C1 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 3.16 or later is necessary to control C1 cameras.

C1 camera drivers for 3^rd party software packages also need to be updated to work with C1 cameras. Minimum versions for respective drivers are:

• ASCOM drivers version 4.10

• 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.

First light images

The very first prototype of C1-3000 camera was used by renowned astro-photographer Martin Myslivec. He used the Borg 77ED refractor telescope on the EQ6 mount co capture several unguided exposures. Despite we understand Martin is highly skilled and experienced astro-photographer, the performance of C1 camera is very good also for deep-sky imaging.

The M31 Great Andromeda galaxy is a stack of 197 exposures 20 s long (approximately 1 hour and 5 minutes of total exposure time). No image processing was performed beside individual frame calibration and slightly non-linear stretching.

The M42 Great Orion nebula image was combined from two sets of exposures (kind of HDR image processing). Faint nebulosity, far from the image center, was acquired using 100 exposures 20 s long (approximately 33 minutes of total exposure time). The very bright central part of the nebula was captured with only 2 s long exposures (again 100 of them), which leads to approximately 3 minutes of total exposure time. The very short exposures allowed to perfectly capture the 4 central stars (called Trapezium) without over-exposing them.

The image of M45 Pleiades is a combination of 218 exposures 20 s long (approximately 1 hour and 12 minutes of total exposure time). Again, no image processing was performed, only the calibration and slight non-linearly stretch was performed.