C5 cameras are made in two versions:

• Asymmetrical version marked C5A

• Symmetrical version marked C5S

Asymmetrical C5A variant look reveals the same time-proven design school of the C3 and C4 series in both outer shape and internal construction. The front cross-section of the C5A cameras is the same as the C3 and C4 series, although the used sensors are much larger. C5 head thickness corresponds to the thickness of the Enhanced Cooling versions of the earlier models.

Asymmetrical models also employ mechanical shutter, allowing to capture dark or bias frames without a necessity to cover the telescope aperture.

Symmetrical C5S variant main purpose is not to exceed the central obstruction of reflecting telescopes with the camera located in the primary focus. The asymmetrical variant typically overhangs the central obstruction of smaller telescopes (with ~0.4 m primary mirror diameter), despite the central obstruction of wide-field telescope is rather big.

Due to mechanical constrains, the symmetrical model lacks the mechanical shutter.

Compared to C3 and C4 cameras, both C5A and C5S series feature completely redesigned air cooling — more powerful and also quieter than even the EC variants of the C3 and C4. Also, the supplied AC/DC brick power adapter is more powerful and employs more robust power plug.

Usage of large sensors required completely new design of the telescope interface and the C5 series offers M68 × 1 threaded adapter only on the smaller 100 MPx C5 variant. Large 150 MPx version of the C5 standardizes on the M85 × 1 thread on the tiltable adapter. Like in the case of the C4 series, the internal filter wheel is not an option, external filter wheels are necessary and the C5 camera are equipped to control new EFW-5XL series of filter wheels. Huge sensors require huge 65 × 65 mm square filters and EFW-5XL-5 is designed for five such filters. The EFW-5XL-7 filter wheels for seven smaller 50 × 50 mm square filters are available for 100 MPx C5 variant with smaller sensor.

Rich software and driver support allow usage of C5 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 C5 camera with broad variety of camera control programs.

The C5 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. 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.

C5 cameras are designed to be attached to host PC through very fast USB 3.0 port. While the C5 cameras remain compatible with older (and slower) USB 2.0 interface, image download time is significantly longer.

Alternatively, it is possible to use the Moravian Camera Ethernet Adapter device. This device can connect up to four Cx (and CCD based Gx) cameras of any type (not only C5, but also C1, C2, C3 and C4) 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.

Download speed is naturally significantly slower when camera is attached over Ethernet adapter, especially when compared with direct USB 3 connection.

The camera must be connected to some optical system (e.g. the telescope) to capture images. As the C5 cameras offer really large sensors with 67 mm (150 MPx version) and 55 mm (100 MPx version) diagonals, optical system must be capable to cover such large field of view. The camera is designed for 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.

C5 Camera Overview

C5 camera head is designed to be used with or without external filter wheel. The EFW-5XL external filter wheel with 50 × 50 mm filters is suitable for C5A-100M camera only, large sensor C5A-150M model needs EFW-5XL external filter wheel, designed for 65 × 65 mm filters.

Components of C5 Camera system include:

1. C5A or C5S camera head

2. External Filter Wheel “XL” size

3. 7-positions filter wheel for “XL” housing for 50 × 50 mm square filters

   Remark:

   The 50 × 50 mm filters are usable with C5-100M camera, which sensor longer side measures 44 mm. C5-150M camera sensor longer side measures 53.4 mm, so 48 × 48 mm clear openings in the filter wheel partially cover sensor sides.

4. 5-positions filter wheel for “XL” housing for 65 × 65 mm square filters

5. Canon EOS bayonet adapter for the “XL” size External Filter Wheel with 44 mm BFD

6. M68 × 1 threaded adapter, BFD is 35 mm when mounted directly on camera head and 47.5 mm when mounted on EFW

   Remark:

   The M68 × 1 adapter is suitable for C5-100M camera with smaller sensor, the C5-150M version should use greater M85 × 1 adapter not to cause vignetting.

7. M85 × 1 threaded adapter, BFD is 31 mm when mounted directly on camera head and 43.5 mm when mounted on EFW

8. C5-OAG (Off-Axis Guider Adapter) with M85 × 1 thread for the “XL” size External Filter Wheel with 61.5 mm BFD

9. 10 mm long CS-to-1.25" adapter, used to attach CS-mount (C-thread, 12.5 mm BFD) compatible guider cameras to the OAG

10. C1 or C0 guider camera

    Remark:

    Note the mechanical constrains of the C5S camera do not allow usage of the C1 camera, only the smaller C0 cameras can be used with C5S models.

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

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

11. Moravian Camera Ethernet Adapter (x86 CPU)

12. Moravian Camera Ethernet Adapter (ARM CPU)

    Remark:

    The 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.

CMOS Sensor and Camera Electronics

Both C5A and C5S cameras are equipped with Sony IMX rolling shutter back-illuminated CMOS detectors with 3.76 × 3.76 μm square pixels. Despite the relatively small pixel size, the full-well capacity over 50 ke- rivals the full-well capacity of competing CMOS sensors with much greater pixels and even exceeds the full-well capacity od CCD sensors with comparable pixel size.

The used Sony sensors are equipped with 16-bit ADCs (Analog to Digital Converters). 16-bit digitization ensures enough resolution to completely cover the sensor exceptional dynamic range.

C5 camera models include:

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 C5 cameras show 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

C5 cameras are equipped with on-board RAM, capable to hold several full-resolution frames. Downloading of the image to the host computer thus 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.

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.

C5 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.

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 particular 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 C3-61000 full frame is approx. 2.5 s.

Camera gain

Sensors used in C3 cameras offer 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 50,000 / 3.52 = 14,205×

• At gain = 2750, dynamic range is 16,500 / 1.51 = 10,927×

Also, it is worth noting that in reality the noise floor is only rarely 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 limit 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 C5 camera implements 2 × 2 binning mode in hardware in addition to normal 1 × 1 binning. This mode can be turned on and off using the HWBinning parameter 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 and software binning is no longer available. 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.

For CMOS sensors with full 16-bit dynamic resolution, the negative side of binning is limiting of the sensor dynamic range, as for instance only 1/4 of maximum charge in each of the 2 × 2 binned pixels leads to saturation of resulting pixel. CCDs eliminated this effect to some extend by increasing of the charge capacity of the output node and also by decreasing of the conversion factor in binned modes. But such possibilities are not available in CMOS detectors.

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.

As the C5 camera read noise in the maximum dynamic range (gain 0) is around 3.5 ADU, halving it in 2 × 2 binning mode still keeps the read noise above the lower 1-bit limit and at the same time binned pixel will not saturate. For higher binning modes, the noise approaches lower limit, but averaging pixels still protects from pixel saturation, which is more important than possible S/N limitation caused by underflow of read noise.

If we take into account that the image background noise is only rarely defined by the read noise of the sensor, as the noise caused by background sky glow is typically much higher, for 16-bit camera averaging pixels is definitely the better way to bin pixels compared to just adding them. This is why both software and hardware binning modes in the C5 cameras are by default implemented as averaging of pixels, not summing.

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

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 C5 cameras depends on the used sensor type:

• C5A/C5S-100M shortest exposure is 164 μs

• C5A/C5S-150M shortest exposure is 183 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 of both camera models is 200 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).

C5A mechanical shutter

C5A 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 C5A 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 approx. 10 seconds while the shutter is open (this means after a light image exposure), camera firmware closes the shutter to cover the sensor from incoming light.

C5S hardware trigger input

The C5S trigger input allows for external hardware to determine the exact time of exposure start.

The port uses RJ9 (4P4C) four-pin connector. Pins 1 and 2 are connected and have a function of positive pole, pins 3 and 4 are connected to negative pole. The trigger is activated when an external hardware connects pins 1 and/or 2 with pins 3 and/or 4. The trigger input port is electrically isolated from the rest of the camera — power and USB grounds etc.

The maximum current, consumed by the short-circuited trigger port, does not exceed 1 mA.

The trigger input is located on the upper-left portion of the C5S camera back side, just above the power input plug.

GPS exposure timing

C5 cameras can be equipped with GPS receiver module (see the Optional Accessories chapter). The primary purpose of the GPS receiver is to provide precise times of exposures taken with the camera, which is required by applications dealing with astrometry of fast-moving objects (fast moving asteroids, satellites, and space debris on Earth orbit, …).

The GPS module needs to locate at last 5 satellites to provide exposure timing information. Geographic data are available if only 3 satellites are visible, but especially the mean sea level precision suffers if less than 4 satellites are used.

The camera SDK provides functions, allowing users to access precision exposure times as well as geographics location. The SIPS software package main imaging camera control tool window contains the “GPS” tab, which shows the state of the GPS fix.

Determination of exact exposure time is quite complicated because of the rolling-shutter nature of the used sensors. Camera driver does all the calculations and returns the time of the start of exposure of the first line of the image. Still, users interested in precise exposure timing need to include several corrections into their calculations:

• Individual image lines are exposed sequentially. The time difference between start of exposure of two subsequent lines is fixed for every sensor type:

  • C5A/C5S-100M line exposure takes 40.944 μs

  • C5A/C5S-150M line exposure takes 45.833 μs

• If the image is binned, single line of resulting image contains signal from multiple added (or averaged) lines, each with different exposure time start. The exposure start of individual lines of the binned images differs by the single line time difference, multiplied by the vertical binning factor.

• If only a sub-frame is read, it must be considered that the sensor imposes some restrictions to the sub-frame coordinates. If the required sub-frame coordinates violate the sensor-imposed rules, camera driver enlarges the sub-frame region to fully contain desired sub-frame and then crops it by software. The provided start exposure time then concerns the first line actually read from the camera, not the first line of the resulting (software cropped) image.

  For instance, the y-coordinate of the sub-frame must not be lower than 25 lines. If a sub-frame with lower y-coordinate is asked by the user, whole frame is read and cropped by software. Note the camera SDK offers function AdjustSubFrame, which returns the smallest sub-frame, fully containing the requested sub-frame, but also fulfilling the sensor-imposed sub-frame coordinate restriction. If adjusted sub-frame is read, no software cropping occurs and image exposure time concerns the first line of the image. The SIPS software offers the “Adjust Frame” button, which adjusts defined sub-frame.

Always use the latest camera drivers (ASCOM or Camera SDK DLLs in Windows, INDI or libraries in Linux) available on the web. Also, always update the firmware in the Moravian Camera Ethernet Adapter if the camera is connected over Ethernet.

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 fans. 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 airflow is slightly different between C5A and C5S models.

• C5A camera air intake is located on the top side of the camera head; hot air output vents are on the camera back side.

• C5S camera air intake is on the camera bottom and output vents are on top.

The cooling performance 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.

Overheating protection

The C5 cameras are equipped with an overheating protection in their firmware. This protection is designed to prevent the Peltier hot side to reach temperatures above ~50°C sensor cooling is turned off to stop heat generation by the hot side of the Peltier TEC modules.

Turning the overheating protection on results in a drop in cooling power, a decrease in the internal temperature of the camera and an increase in the temperature of the sensor. However, when the camera cools its internals down below the limit, cooling is turned on again. If the environment temperature is still high, camera internal temperature rises above the limit an overheating protection becomes active again.

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, 120 W “brick” adapter is supplied with the camera. Although the camera power consumption does not exceed 60 W, the 120 W power supply ensures noise-free operation.

Mechanical Specifications

Compact and robust camera head measures only 154 × 154 × 76 mm (approx. 6 × 6 × 3 inches).

The head is CNC-machined from high-quality aluminum and black anodized. The head itself contains USB-B (device) connector and 4-pin 12 V DC power plug, no other parts, except a “brick” power supply, are necessary. Another connector on the camera head allows control of optional external filter wheel.

Integrated mechanical shutter of the C5A models allows automatic dark frame exposures, which are necessary for unattended, robotic setups.

C5A camera head front view

Filter wheels or tiltable adapter base are attached to the camera head using six M3 screws around the 70 mm diameter ring.

C5A camera with M85 × 1 threaded adapter

The stated back focal distances (BFD) include corrections for all optical elements in the light path (cold chamber optical window, sensor cover glass, ...), fixed in the camera body. So, stated values are not mechanical, but optical back focal distances. However, no corrections for filters are included, as the thicknesses of various filters are very different.

C5A camera with M68 × 1 threaded adapter

There are two variants of the M68 × 1 adapter available. The version 1 consists of two parts (the base and the M68 threaded ring attached with 5 screws) and thus its total height is greater. The newer M68 × 1 adapter version 2 is machined from one piece and its total height is smaller, which results into shorter total BFD.

C5A camera with Standalone Filter Wheel

While all EFWs from “XS” to “L” size are designed to preserve the very same BFD on all Cx cameras, the SFW naturally increased the BFD because of the design using two overlapping wheels. The resulting BFD depends on the adapter used.

C5A camera with C5-OAG with M85 × 1 thread

C5-OAG is designed to be used with the XL-sized External filter wheels only.

C5S camera head front view

Filter wheels or tiltable adapter base are attached to the camera head using six M3 screws around the 70 mm diameter ring.

C5S camera with M85 × 1 threaded adapter

The stated back focal distances (BFD) include corrections for all optical elements in the light path (cold chamber optical window, sensor cover glass, ...), fixed in the camera body. So, stated values are not mechanical, but optical back focal distances. However, no corrections for filters are included, as the thicknesses of various filters are very different.

C5S camera with M68 × 1 threaded adapter

There are two variants of the M68 × 1 adapter available. The version 1 consists of two parts (the base and the M68 threaded ring attached with 5 screws) and thus its total height is greater. The newer M68 × 1 adapter version 2 is machined from one piece and its total height is smaller, which results into shorter total BFD.

C5S camera with Standalone Filter Wheel

While all EFWs from “XS” to “L” size are designed to preserve the very same BFD on all Cx cameras, the SFW naturally increased the BFD because of the design using two overlapping wheels. The resulting BFD depends on the adapter used.

C5S camera with C5-OAG with M85 × 1 thread

C5-OAG is designed to be used with the XL-sized External filter wheels only.

Filter distance to sensor

It is necessary to know the distance of the filter entrance aperture from the sensor to calculate possible vignetting (partial shielding of the sensor edge parts from the incoming lights). In the case of C5 cameras, this is technically not an “aperture”, as the filters are squares. So, instead of comparing filter aperture diameter to sensor diagonal, filter hole linear dimension must be compared longer side of the sensor.

The 7-positions filter wheel for 50 × 50 mm filters entrance dimension is 48 mm, 5-positions filter wheel for 65 × 65 mm filters entrance dimension is 63 mm. The C5A-100M sensor longer side measures 43.86 mm, while the C5A-150M sensor longer side measures 53.42 mm.

Optional accessories

Various accessories are offered with C5 cameras to enhance functionality and help camera integration into imaging setups.

External filter wheels

The C5 camera contains electronics and an 8-pin connector on the camera head to control filter wheels. As the mechanical interface of the C5 cameras, intended to attach filter wheels, differs from the interface on the C3 or C4 cameras (see the chapter Camera head front view of the Mechanical Specification section for details), C5 cameras are not compatible with the “M” or “L” external filter wheels intended for C3 or C4 lines. New “XL” size external filter wheel is designed especially for the C5 series.

The ”XL” filter wheel housing can accommodate two filter wheels:

• 5-positions filter wheel for 65 × 65 mm filters

• 7-positions filter wheel for 50 × 50 mm filters

Standalone filter wheels

The external filter wheel diameter has construction limits, it is not possible to simply increase both EFW shell and filter wheel itself. The diameter and weight would be so big, that usage of such wheels would not be practical.

Natural solution of this problem is placing of two smaller filter wheels beside each other. The total number of filter positions is lower than the sum of positions in both wheels from obvious reasons: one position in each wheel must remain empty (clear) and it is set as an actual position when a filter from the other wheel is to be used not to interfere with it. So, if for instance two filter wheels with five positions each are used, we denote such wheel as “8+Clear” positions. This means four positions in both wheels may be used for any filter, which makes 8 total filter positions. When both filter wheels are set to index 0 (the clear position), one additional clear position is added to the total number of filter positions.

The Standalone Filter Wheel (SFW), compatible with C5 cameras, comes in the “XL” flavor, which indicates it is even greater than the larges “L” sized EFW available. Number of available positions depends on filter size:

• 8+Clear positions for 65 × 65 mm square filters, suitable for C5 cameras (both asymmetrical C5A and symmetrical C5S variants)

• 12+Clear positions for 50 × 50 mm square filters, suitable for C5-100M cameras (with some vignetting over the sensor short edge)

The SFW filter wheels are equipped with 12 V DC 5.5/2.5 mm power plug as well as USB 1.1 data connection. Latest SIPS v4.1 and later software contains native driver for these wheels, as well as Moravian Camera Ethernet Adapter firmware, ASCOM drivers for windows, Linux libraries and INDI/INDIGO drivers are available etc. Also, the Moravian Camera SDK contains libraries, headers and API description allowing to control the SFW from other software packages as well as from Python etc.

Telescope adapters

There are basically only two types of telescope adapters, available for C5 cameras:

• M85 × 1 threaded adapter, intended for both C5A-100M and C5A-150M camera models. This adapter is also equipped with eight M3 threaded holes arranged around the 91 mm diameter circle, providing alternative possibility to attach the C5 camera to the optical system.

• M68 × 1 threaded adapter, suitable for C5A-100M camera only due to limited aperture, possibly causing vignetting of the large sensor of C5A-150M camera.

Both adapters have adjustable tilt and both can be mounted either on the adapter base on the camera head or on the External filter wheel front plane.

Off-Axis Guider adapter

C5 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.

The C5-OAG offers the M85 × 1 thread on the telescope side. The back focal distance is 61.5 mm.

The C5-OAG is designed for cameras using the XL-size external filter wheel. The guiding camera will not be able to reach focus is the OAG is mounted directly to the camera head.

OAG guider port is compatible with C0 and C1 cameras when mounted on the C5A camera. Mechanical constrains of the C5S camera head allows usage of only smaller C0 models. It is necessary to replace the CS/1.25” adapter with short, 10 mm variant. 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 C5-OAG.

GPS receiver module

The C5 cameras can be equipped with an optional GPS receiver module, which allows very precise timing of the exposure times. Geographic location data are also available to the control software through specific commands.

The used GPS receiver is compatible with GPS, GLONASS, Galileo and BeiDou satellites.

The GPS receiver can be attached to the back side of the camera head. If the GPS module is removed, the GPS port is covered with a flat black cover.

Spare desiccant containers

The C3 cameras are supplied with silicagel container, intended to dry the sensor cold chamber. This container can be unscrewed and desiccant inside can be dried in the oven (see the camera User's Manual).

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. Containers intended for enhanced cooling cameras are prolonged as the camera thickness is greater in the case of this variant.

It is possible to order spare container, which makes desiccant replacement easier and faster. It is possible to dry the spare container with silicagel and then only to replace it on the camera. Spare container is supplied including the air-tight cap.

Spare container can be supplied also in a variant that allows manipulation without tools. But this container is longer and exceeds camera outline. If the space behind the camera is not critical, this container can make desiccant exchange even easier.

Moravian Camera Ethernet Adapter

The 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 practically unlimited distance.

Moravian Camera Ethernet Adapter devices are 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 (like C0) or latest versions or existing series (like C1 version 3).

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.

Shipping and Packaging

C5 cameras are supplied in the foam-filled, hard carrying case containing:

• Camera body with a user-chosen telescope adapter.

• A 100-240 V AC input, 12 V DC output “brick” adapter with 1 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 C5 cameras.