C1+ cameras with global shutter CMOS sensors are designed to be able to operate from USB power lines only. However, some functions are available only if external 12 V DC power supply is connected. C1+ functions equal to C1 cameras when powered from USB only:

• Image acquisition.

• Mount guiding through standard “autoguider” 6-pin connector.

When a 12 V DC power is plugged in, C1+ camera functions are extend with:

• Active and regulated sensor cooling with Peltier cooler.

• Ability to control external filter wheel.

The C1+ cameras with rolling shutter CMOS sensors always require the 12 V DC power.

Still, C1+ capabilities lack some functionality, available in larger and heavier C2 cameras only:

• C1+ have no mechanical shutter, necessary for automatic dark and bias frame acquisition in remote or robotic setups.

• C1+ lack the possibility to use internal filter wheel.

• C1+ cooling performance is slightly lower than in the case of C2, but the sensor temperature difference is only a few degrees Celsius.

Mechanical design of this series makes it fully compatible with vast range of telescope adapters a external filter wheels, Camera Ethernet adapters, etc.

Rich software and driver support allows usage of C1+ camera without necessity to invest into any 3^rd party software package thanks to included free SIPS software package. However, ASCOM (for Windows) and INDI (for Linux) drivers, shipped with the camera, provide the way to integrate C1+ camera with broad variety of camera control programs.

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.

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 Overview

C1+ camera head is designed to be as small and compact as a cooled camera with rich features and compatible with broad set of accessories can be.

C1+ cameras are equipped with tiltable telescope interface and threaded holes for mounting on tripod or dovetail bar. They are also compatible with external filter wheels designed for larger C2 cameras — camera head contains connector to control filter wheel. If the external filter wheel is used, the tiltable mechanism on the camera head is inactive and tiltable adapters for external filter wheels are used instead. Therefore, C1+ cameras can utilize vast range of telescope and lens adapters including off-axis guider adapters.

There are two sizes of the External filter wheels, each capable to accept multiple sizes of filters, available for the C1+ 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.

Components of C1+ Camera system include:

1. C1+ camera head with C1 compatible adapter with M42 × 0.75 thread, 18.5 mm BFD

2. C1+ camera head with C2 compatible adapter with four M3 threaded holes 44 mm apart and M48 × 0.75 thread, 16.5 mm BFD

   Remark:

   When used without spring and pushing screws, this adapter also works as base for External filter wheels.

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 or M42 × 0.75 (T2) thread

7. C1 compatible Nikon bayonet lens adapter

8. C1 compatible Canon EOS bayonet lens adapter

9. C1 compatible M42 × 0.75 (T-thread) threaded adapter, 55 mm BFD

10. C1 compatible M48 × 0.75 threaded adapter, 55 mm BFD

11. C2 compatible M42 × 0.75 (T-thread) or M48 × 0.75 threaded adapter, 55 mm BFD

12. C2 compatible Canon EOS bayonet lens adapter

13. C2 compatible Nikon bayonet lens adapter

14. Camera Ethernet Adapter (x86 CPU)

15. 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.

16. 8-positions external filter wheel “XS” for 1.25”/D31 mm filters

17. 7-positions external filter wheel “XS” for D36 mm filters

18. 12-positions external filter wheel “S” for 1.25”/D31 mm filters

19. 10-positions external filter wheel “S” for D36 mm filters

20. 7-positions external filter wheel “S” for 2”/D50 mm filters

C1+ with global shutter CMOS Sensors

C1+ camera models equipped with Sony IMX global shutter CMOS detectors have 3.45 × 3.45 μm or 4.50 × 4.50 μm square pixels.

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 C1+ cameras are available depending on the available dynamic range (bit-depth of the digitized pixels) and pixel size:

• C1+ 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.

• C1+ 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.

• C1+ 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.

C1+ camera models with 3.45 × 3.45 μm pixels and 8- and 12-bit digitization:

C1+ camera models with 3.45 × 3.45 μm pixels and 12-bit digitization only:

C1+ camera models with 4.50 × 4.50 μm pixels and 12-bit digitization only:

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 variable stars etc.

Download speed

As already noted, there are two lines of C1+ 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 C1+ 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 C1+ 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 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.

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

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).

C1+ with rolling shutter CMOS Sensors

C1+ series of CMOS cameras with Sony IMX rolling shutter CMOS detectors currently contain single model with Sony IMX533 sensor with pixel size 3.76 × 3.76 μm:

As opposed to global-shutter sensors, rolling-shutter sensors expose individual lines in sequence.

Camera Electronics

Controlling of the rolling shutter sensors differs significantly from controlling of the global shutter sensors and thus the camera C1+9000 internals are quite different from other C1+ models.

The C1+9000 contains 256 MB of onboard memory, capable to store up to 14 full-resolution frames. Camera API allows for sequential exposures, during which short-exposure images are stored into memory possibly faster than the host computer is able to read them. Sequential exposures are paused when the internal memory is filled with images, not yet read by the host PC. As explained earlier, rolling shutter sensors are capable to perform image exposure while digitizing the previous image.

Sensor linearity

The IMX533 sensor used in C1+9000 (and also C2-9000) shows very good linearity in response to light. This means the camera can be used for advanced research projects, like the photometry of variable stars and transiting exoplanets etc.

Download speed

Thanks to C1+9000 onboard RAM, downloading of the image to the host computer does not influence image digitization process, as the download only transfers already digitized images from camera memory.

Time needed to digitize and download single full frame depends on USB connection type.

• Full-frame, USB 3.0 (5 Gbps): 0.06 s

• Full-frame, USB 2.0 (480 Mbps): 0.40 s

If only a sub-frame is read, time needed to digitize and download image is naturally lower. However, the download time is not cut proportionally to number of pixels thanks to some fixed overhead time, independent on the sub-frame dimensions.

• 1024 × 1024 sub-frame, USB 3.0 (5 Gbps): 0.02 s

• 1024 × 1024 sub-frame, USB 2.0 (480 Mbps): 0.05 s

The C4+9000 camera electronics supports in-camera 2 × 2 binning. If this binning mode is used, download speed increases because of less amount of data read from camera.

• Full-frame 2 × 2 binning, USB 3.0 (5 Gbps): 0.03 s

• Full-frame 2 × 2 binning, USB 2.0 (480 Mbps): 0.11 s

Download speed when using the Moravian Camera Ethernet Adapter depends if the 100 Mbps or 1 Gbps Ethernet is used, if USB 2 or USB 3 is used to connect camera to Ethernet Adapter device, but also depends on the network utilization etc. When the camera is connected to the Ethernet Adapter using USB 3 and 1 Gbps Ethernet is directly connected to the host PC, download time of the C1+9000 full frame is less than 0.5 s.

Camera gain

Rolling shutter sensor used in C1+ cameras offers programmable gain from 0 to 36 dB, which translates to the output signal multiplication from 1× to 63×.

Camera driver accepts gain as a number in the range 0 to 4030, which corresponds directly to sensor register value. This number does not represent gain in dB nor it is an exact gain multiply. However, the driver offers a function, which transforms the gain numerical value to gain expressed in dB as well as multiply. Some selected values are shown in the table:

Conversion factors and read noise

Generally, many sensor characteristics depend on the used gain. Also, the used sensors employ two conversion paths. One path offers very low read noise, but cannot utilize full sensor dynamic range. Another conversion path offers maximum pixel capacity, but at the price of higher read noise. The cross point is set to gain 3× (approx. 10 dB), where the full well capacity drops from more than 50 ke- to ~17 ke-. The read noise then drops from ~3.2 e- RMS to ~1.5 e- RMS.

Sensor dynamic range, defined as full well capacity divided by read noise, is greatest when using gain 0, despite somewhat higher read noise:

• At gain = 0, dynamic range is 50,800 / 3.81 = 13,333×

• At gain = 2750, dynamic range is 16,500 / 1.55 = 10,645×

Also, it is worth noting that in reality the noise floor is not always defined by read noise. Unless the camera is used with very narrow narrow-band filter (with FWHM only a few nm) and under very dark sky, the dominant source of noise is the sky glow. When the noise generated by sky glow exceeds approximately 4 e- RMS, extremely low read noise associated with gain set to 2750 or more is not utilized and dynamic range is unnecessarily limited by the lowered full well capacity.

So, which gain settings is the best? This depends on the particular task.

• Gain set to 2750 can be utilized if imaging through narrow-band filter with appropriately short exposures, so the background noise does not exceed the read noise. This is typical for aesthetic astro-photography, where the lowered full well capacity does not negatively influence the result quality.

  But even without narrow-band filters, the extremely low read noise allows stacking of many short exposures without unacceptable increase of the stacked image background noise, caused by accumulation of high read noise of individual exposures.

• Gain set to 0 offers maximum full well capacity and the greatest sensor dynamic range, which is appreciated mainly in research applications. Pass-bands of filters used for photometry are relatively wide and dominant source of noise is the sky glow.

  But also for RGB images, used for aesthetic astro-photography, higher dynamic range allows longer exposures while the bright portions of the nebulae and galaxies still remain under saturation and thus can be properly processed.

Binning

The camera driver and user’s applications offer wide variety of binning modes up to 4 × 4 pixels as well as all combinations of asymmetrical binning modes 1 × 2, 1 × 3, 1 × 4, 2 × 4 etc. To allow such flexibility, binning is performed only in the camera driver (software binning) and does not rely on the limited capabilities of the hardware binning.

The negative side of software binning is the same download time like in the case of full-resolution 1 × 1 mode. For typical astronomy usage, the small fraction of second download time is irrelevant, but for applications sensitive to download time, the hardware 2 × 2 binning can be useful.

Hardware binning

The C1+9000 camera implements 2 × 2 binning mode in hardware in addition to normal 1 × 1 binning.

Hardware binning can be turned on and off using the parameter HWBinning in the 'cXusb.ini' configuration file, located in the same directory like the 'cXusb.dll' driver DLL file itself.

[driver]
HWBinning = true

When the HWBinning parameter is set to true, the in-camera hardware binning is used. This mode brings faster download time, but also introduces several restrictions:

1. Maximal binning is limited to 2 × 2, higher binning modes are not available.

2. Asymmetrical binning modes (1 × 2, 2 × 1, ...) are not allowed.

Adding vs. averaging pixels

The traditional meaning of pixel binning implies adding of binned pixels. This originated in CCD sensors, where pixel charges were literally poured together within the sensor horizontal register and/or the output node. Binning with CMOS sensors can behave differently, pixels can be either added or averaged.

In theory, the resulting S/N ratio of binned pixel remains the same regardless if we add or average them. Let's take for example 2 × 2 binning:

• If we add 4 pixels, signal increases 4-times and noise increases 2-times — three additive operations increase noise by √((√2)^2×(√2)^2 ). Resulting S/N increases 2-times, but only until the sum of all pixels is lower than the pixel capacity.

• If we average 4 pixels, signal remains the same but the noise is lowered to 1/2 as noise is averaged √((√2)^2×(√2)^2 )/4. Resulting S/N also increases 2-times, but only until the noise decreases to lowest possible 1-bit of dynamic range.

But in reality, resulting S/N ratio can be affected either by overflow (saturation) of resulting pixel when adding binned pixels or by read noise underflow (dropping below 1 bit) when averaging them.

While the bigger siblings of the C1+9000 camera (C1×, C3 and C5) utilize CMOS sensors with full 16-bit dynamic resolution, the sensor used in C1+9000 offers only 14-bit conversion. So, up to 4 pixels (2 × 2 binning) can be added and still the resulting pixel cannot overflow the 16-bit dynamic range of each 2 bytes long pixel. This is why the default binning behavior of the C2-9000 camera uses pixel adding instead of averaging on both software binning and in-camera (hardware) binning.

However, both software and hardware binning modes can be switched to sum binned pixels instead of average them by the BinningSum parameter in the 'cXusb.ini' configuration file:

[driver]
BinningSum = true

Let’s note there is one more possibility to bin pixels — in the application software. This time binning is not performed in camera hardware nor in the camera driver. Full resolution 1 × 1 image is downloaded from the camera and software itself then performs binning. The SIPS software adds pixels instead of averaging them, but at the same time SIPS converts images from 16-bit to 32-bit dynamic range. This means S/N of the binned images always increases, pixels never saturate and read noise newer approaches lower limit. The negative side of this option is two-time bigger images.

Binning in photometry

Saturated pixels within bright stars are no issue for aesthetic astro-photography, but photometry measurement is invalid if any pixel within the measured object reaches maximum value, because it is not possible to determine the amount of lost flux. Software performing photometry (e.g. the SIPS Photometry tool) should detect saturation value and invalidate entire photometric point not to introduce errors.

But binning efficiently obliterates the fact that any of the binned pixels saturated (with the exception of all binned pixels reached saturation value). So, using of binning modes for research applications (photometry and astrometry) can lead to errors caused by lost flux in saturated pixels, which cannot be detected by the processing software due to binning.

This is why the behavior of both software and hardware binning modes is user-configurable through the BinningSaturate parameter in the 'cXusb.ini' configuration file:

[driver]
BinningSaturate = true

If the BinningSaturate parameter is set to true, resulting binned pixel is set to saturation value if any of the source pixels is saturated. For aesthetic astro-photography, keeping this parameter false could result into slightly better representation of bright star images, but for research applications, this parameter should always be set to true.

Exposure Control

The shortest theoretical exposure time of the C1+9000 camera is 49 μs. However, such short exposures have no practical application, especially in astronomy. The camera firmware rounds exposure time to a multiply of 100 μs intervals, so in reality the shortest exposure time is also 100 μs.

There is no theoretical 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).

Cooling and power supply

As mentioned in the introduction, C1+ cameras can operate only with USB power. Camera is then capable to acquire images and to control (guide) telescope mount via “autoguider” port. However, active sensor cooling (as well as filter wheel operation) is available only if external 12 V DC power supply is connected.

Regulated thermoelectric cooling is capable to cool the CMOS sensor more than 40 °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 thermometer measures directly the temperature of the CMOS sensor. 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 25 W, the 60 W power supply ensures noise-free operation.

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 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

Compact and robust camera head measures only 78 × 78 × 80 mm (approx. 3.1 × 3.1 × 3.2 inches). The head is CNC-machined from high-quality aluminum and black anodized. The head itself contains USB-B (device) connector, Autoguider port connector, connector for External Filter Wheel and 12 V DC power plug.

The front side of the C1+ camera body is not intended for direct attachment of the telescope/lens adapter. It is instead designed to accept tiltable adapter base, on with the telescope and lens adapters are mounted. There are two variants of adapters available:

• C1 compatible adapter base with M42 × 0.75 (T-thread) and back focal distance (BFD) 18.5 mm.

  The 18.5 mm BFD equals to C1 camera with M42 × 0.75 adapter. Numerous extension adapters are available for C1 cameras, like M48 × 0.75 thread or M42 × 0.75 thread (T-adapter) with 55 mm BFD, Canon EOS and Nikon bayonets etc. All these adapters are then compatible also with C1+ cameras.

  As opposed to C1 series, these adapters are mounted on the tiltable base and therefore can adjust optical axis if necessary.

• C2 compatible adapter base with 16.5 mm BFD. This adapter contains four M3 threaded holed 44 mm apart and also M48 × 0.75 thread.

  Note the 16.5 mm BFD equals to BFD of large cooled C2 cameras without filter wheel. Therefore, it is possible to attach all adapters for C2 cameras as well as external filter wheels to this adapter.

  When used with External filter wheel, this adapter lacks the tilting spring and pushing screws, which are not necessary as the External filter wheel itself offer tiltable adapters intended for C2 cameras.

  Remark:

  Of course, this adapter base can be used without External filter wheel and then it provides M48 × 0.75 with very short 16.5 mm BFD.

C1+ Camera with C1 compatible adapter base

C1+ Camera with C2 compatible adapter base

C1+ Camera with “XS” External Filter Wheel

C1+ cameras can be equipped with the same external filter wheels like the C2 cameras. In such case the C2 compatible adapter has to be used as a base for the External filter wheel.

If the external filter wheel is used, tiltable adapters for C2 or G2 Mark II cameras have to be used with it.

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.

Optional accessories

Various accessories are offered with C1+ cameras to enhance functionality and help camera integration into imaging setups.

Telescope adapters

Telescope and lens adapters, intended for usage with C1+ cameras, are of two kinds:

• Adapters for C1 cameras. These adapters are mounted using M42 × 0.75 thread with 18.5 mm BFD. C1 compatible adapter base must be mounted on the C1+ camera head.

• Adapters for C2 cameras. C2 camera adapters are mounted on a tiltable base, which is manufactured on external filter wheel or on a standalone base if no filter wheel is used. Filter wheel or adapter base is mounted using four M3 threaded holes on a plate 16.5 mm from the sensor.

  • If a C2 adapter has to be used without filter wheel, a stack of two adapter bases must be used on C1+ camera — C2 compatible adapter base for C1+ camera and C2 adapter base on it. However, such combination is superfluous despite it is possible, as majority of C2 adapter have an equivalent designed for C1 camera and thus can be used with C1 compatible adapter base.

  • The same tiltable adapter base is manufactured on the front plate of the external filter wheels. External filter wheel needs the C2 compatible adapter base attached to C1+ camera. Then all C2 adapters can be used.

For illustration of adapter options, see the figure in the C1+ Camera Overview chapter.

Adapters for C1+ cameras with C1 compatible adapter base

Adapters are mounted to the C1 compatible adapter base, which provide titling mechanism.

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

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

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

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

Adapters for C1+ cameras with C2 compatible adapter base and external filter wheel

C1+ uses the same External filter wheels like the C2 series. These External filter wheels are equipped with tiltable base, intended for adapters.

• 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 BFD.

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

• M48 × 0.75 with 55 mm BFD — adapter with inner thread M48 × 0.75, preserves 55 mm BFD

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

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

Attaching camera head to telescope mount

C1+ camera heads are equipped with “tripod” thread (0.25”) on the bottom side. 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.

Another possibility is to use four metric M4 threaded holes, also located on the bottom side of the camera head.

Tool-less desiccant containers

C1+ cameras employ the same desiccant container like the larger C2 and standard cooling C3 and C4 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 (or for just a coin), 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.

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

Always use the latest versions of the system driver package for both Windows and Linux system. Older versions of drivers may not support new camera models or latest versions or existing series.

If the camera is controlled through the Moravian Camera Ethernet Adapter, make sure the device firmware is updated to the latest version available.

Also, always use the latest version of the SIPS software package, older versions may not support latest cameras correctly. If a driver for 3^rd party software package is used (e.g. ASCOM or INDI drivers), always update the driver to the latest available version.

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.

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.

Drivers for 3^rd party programs

Regularly updated Sofware Development Kit for Windows allows to control all cameras from arbitrary applications, as well as from Python scripts etc.

There are ASCOM standard drivers available together with native drivers for some 3^rd party programs (for instance, TheSkyX, AstroArt, etc.). Visit the download page of this server to see a list of all supported drivers.

Libraries and INDI standard drivers for 32-bit and 64-bit Linux working on x86 and ARM processors are available as well. Also drivers for TheSkyX running on macOS are supplied with all cameras.