Moravian instruments, Inc., source: https://www.gxccd.com/art?id=554&lang=409, printed: 21.4.2019 18:14:54
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|New C1 series of CMOS guiding, Moon/planetary and entry-level deep-sky cameras||Updated: 16.4.2019|
|Moravian Instruments introduces new line of small and affordable cameras intended for automatic guiding, but also for Moon and planetary imaging. Higher models of C1 line of cameras are also suited for entry-level imaging of deep-sky objects and due to very linear response to light, even basic research projects in photometry and/or astrometry can use C1 cameras. Very fast download through USB3 interface, high sensitivity and low read noise of the used CMOS sensors help to achieve good results in a short time.|
The C1 line of cameras is based on Sony IMX CMOS sensors. Cameras are designed to be small and lightweight, yet robust due to CNC-machined shell. The C1 camera series currently comprise of 3 models:
The telescope/lens interface conforms to CS-mount standard (C-mount lens thread with shortened 12.5 mm back focal distance). This makes the C1 line compatible with vast number of CCTV lens and adapters.
The C-mount standard uses the same thread, only the back focal distance is 17.5 mm, which is 5 mm longer compared to short CS version. Simple 5 mm thick threaded ring enables C1 cameras to use lenses designed for C-mount.
The C-mount to 1.25" barrel adapter allows inserting of C1 camera instead of telescope eyepiece and enjoying digital images of astronomical and also terrestrial objects. Short (just 10 mm) version of the C-mount to 1.25" adapter makes the C1 camera fully compatible with all Off-Axis Guider adapters, used with larger cooled Gx and Cx series of cameras.
Despite C1 camera is typically fixed on the telescope through its telescope/lens adapter, the camera body is also equipped with standard 0.25" tripod thread as well as four metric M3 threads on its bottom side.
USB3 connector is used to control the camera and download images as well as to provide power to it. Standard 6-pin autoguider port is located just beside the USB3 connector.
Autoguider port of C1 cameras was enhanced to operate properly also with mounts, which do not strictly follow specification of autoguider port introduced by SBIG ST4 guider (mounts made by Synta, mounts made in Europe or in the States always operated properly).
The very high speed USB3 interface ensures even a multi-megapixel image download time in the order of hundredths of second. Still, USB3 interface operates reliably when the cameras is relatively close to the host computer (USB3 cable length limit for reliable operation is around 2 or 3 meters). But C1 cameras are fully compatible with USB2 cables and PC interfaces, allowing much longer connection between camera and host PC (5 m single cable, a few tens of meters with active hubs/repeaters).
CMOS sensors are capable to digitize images very fast. But also camera electronics has to be able to re-arrange image data and send them to the host PC very quickly not to slow-down the entire system. And fast electronics generates heat, which is a general rule known to every PC enthusiast (the faster is the PC the better cooling is necessary to keep it at proper working temperature). This is why we paid great attention to temperature management of C1 cameras despite this series is not equipped with active (Peltier) cooling.
The C1 camera case is equipped with a small fan, exchanging the air inside the shell. What's more, there is a small heat sink inside the case, removing the heat from the CMOS sensor itself. All this ensures the sensor temperature is kept only a few degrees Celsius above the environment air temperature. This keeps the dark current as low as possible. When taking into account that the dark current doubles with every 6 or 7 degrees Celsius and the sensor temperature can be up to a few tens degrees Celsius above environment temperature in the case of closed designs, the dark current limitation is very important.
Camera allows selection of two read modes — very fast 8-bit and somewhat slower (but still very fast) 12-bit. Unfortunately, A/D converters are integrated with the sensor chip in the case of CMOS detectors, so ADC resolution is defined by the CMOS manufacturer and camera designer cannot influence this. But at the same time IMX CMOS sensors used in C1 cameras offer very low read noise (around 2 e- RMS), so the dynamic range is not that worse compared with CCD cameras equipped with 16-bit ADC.
To our surprise the sensor response to light is perfectly linear. This means the camera can be used also for entry-level research projects, like for instance photometry or brighter variable stars etc.
The very first prototype of C1-3000 camera was used by renowned astro-photographer Martin Myslivec. He used the Borg 77ED refractor telescope on the EQ6 mount co capture several unguided exposures. Despite we understand Martin is highly skilled and experienced astro-photographer, the performance of C1 camera is very good also for deep-sky imaging.
The M31 Great Andromeda galaxy is a stack of 197 exposures 20 s long (approximately 1 hour and 5 minutes of total exposure time). No image processing was performed beside individual frame calibration and slightly non-linear stretching.
The M42 Great Orion nebula image was combined from two sets of exposures (kind of HDR image processing). Faint nebulosity, far from the image center, was acquired using 100 exposures 20 s long (approximately 33 minutes of total exposure time). The very bright central part of the nebula was captured with only 2 s long exposures (again 100 of them), which leads to approximately 3 minutes of total exposure time. The very short exposures allowed to perfectly capture the 4 central stars (called Trapezium) without over-exposing them.
The image of M45 Pleiades is a combination of 218 exposures 20 s long (approximately 1 hour and 12 minutes of total exposure time). Again, no image processing was performed, only the calibration and slight non-linearly stretch was performed.
The C1 cameras will be available very early next year (January 2019). More sophisticated, cooled C2, C3 and C4 series of CMOS based cameras, compatible with very rich set of accessories of the Gx Mark II cameras, will follow soon. We will keep you informed.