Moravian Instruments CG-5000 (IMX250) CMOS Planetary and Guiding Camera (CG-5000)

Moravian Instruments CG-5000 (IMX250) CMOS Planetary and Guiding Camera 

The C0, CG, and C1 series cameras with global shutter CMOS sensors were designed to be small, lightweight imagers for Moon and planets and for automatic telescope guiding. With proper image calibration, these cameras provide surprisingly good results also in entry-level deep-sky imaging. The used CMOS sensors response to light is linear up to very close to saturation point. So, the C0, CG, and C1 cameras can be used for some entry-level scientific applications for instance in the variable star research etc.

Overview

The C0, CG, and C1 cameras share majority of features, like the used sensors, USB interface, autoguider port, etc. At the first view, the only difference is the size and shape of the camera body.

C0 Camera

The main differentiating feature of the CG series is the flattened camera shape.

CG camera

Greater dimensions of the C1 models allowed adding of some features, not available on the C0 cameras, like cooling fan and mounting threaded holes.

C1 Camera

Sometimes the C0 or C1 camera cannot be used on OAG because of its shape. Both C0 and C1 cameras exceed the front plane, defined by the OAG front thread, and thus they can possibly interfere with the telescope's rear mounting interface. The CG cameras are designed not to exceed the OAG in the front. But otherwise, the CG cameras are essentially the C0 ones in the flat casing.

CMOS Sensor

C0, CG, and 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 camera lines are available depending on the available dynamic range (bit-depth of the digitized pixels):

• 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.

• 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.

Camera models with 8- and 12-bit digitization:

Note the CG series do not offer the largest 12 MPx sensor variant, as it is primarily designed for auto-guiding, not imaging.  

Camera models with 12-bit digitization only:

PC Control

The C0, CG, and 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. Note : 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. Note : Only certain software packages are currently supported on Mac.

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 C0, CG, and 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.

Download speed

As already noted, there are two lines of C0, CG, and 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 C0, CG, and 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 C0, CG, and 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.

Exposure control

C0, CG, and 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).

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. C0, CG, and C1 cameras were designed especially with automatic mount guiding on mind.

The guiding 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.

The C0, CG, and 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 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 C0, CG, and 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:

1	R.A. + (Right)
2	Dec + (Up)
3	Dec – (Down)
4	R.A. – (Left)
5	Common (Ground)
6	Not connected

Telescope / lens Adapter

The CG cameras are supplied with CS-mount adapter only. 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.

CG Camera Dimensions

CG camera head with CS-mount adapter front view dimensions (left) and side view dimensions and Back Focal Distance (right)

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 3rd 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.

Technical Specifications

Models 

Camera models with 8- and 12-bit digitization:

Camera models with 12-bit digitization only:

Mechanical Dimensions

In the Box

• Camera Body CG-5000 (IMX250)
• CS Adapter

Warranty & Manuals

Moravian Warranty