TO EXPLORE THE UNKNOWN UNIVERSE
NGC 6888 and bubble soap nebula
APOD 2023 Sep 04
Imaging Camera QHY268M
Integration 44 hours 30 min
Telescope: Askar FRA600
Mount: iOptron CEM40
QHY294M Pro Astronomy Camera is a 4/3-inch back-illuminated camera, equipped with Sony IMX294 (Color) and IMX492 (Mono) sensor.
*Shipment Expenses，Customs or Other Taxes Not Included
The new QHY294 Pro is a 4/3-inch back-illuminated camera, equipped with Sony IMX294 (Color) and IMX 492 (Mono) sensor. The 294 Pro has 11.7 MP at 4.63um, 14-bits A/D. The IMX294 and IMX492 chips have 46.8 million 2.315um pixels, which Sony 2×2 bins on-chip to create the sensor’s advertised 11.7 million 4.63um pixel array. The QHY294 Pro series camera is capable of locking and unlocking the on-chip binning to provide two readout modes. The first mode reads the sensor “locked” mode to produce 11.6mp images with 4.63um pixel size and 14 bits per pixel. The second read mode unlocks the binning to produce 46.8mp images with 2.315um pixel size at 12 bits per pixel.
The QHY294 Pro CMOS sensor has a dual gain mode, HGC (high gain) and LGC (Low gain). The QHY294 Pro will switch the two modes automatically when the gain is set to 1600 you will get the benefits of the ultra low read noise (1e- to 1.6e-) of the HGC mode and a full well capacity of about 14.5ke- at the switch point setting.
One benefit of the back-illuminated CMOS structure is improved full well capacity. In a typical front-illuminated sensor, photons from the target entering the photosensitive layer of the sensor must first pass through the metal wiring that is embedded just above the photosensitive layer. The wiring structure reflects some of the photons and reduces the efficiency of the sensor.
In the back- illuminated sensor the light is allowed to enter the photosensitive surface from the reverse side. In this case the sensor’s embedded wiring structure is below the photosensitive layer. As a result, more incoming photons strike the photosensitive layer and more electrons are generated and captured in the pixel well. This ratio of photon to electron production is called quantum efficiency. The higher the quantum efficiency the more efficient the sensor is at converting photons to electrons and hence the more sensitive the sensor is to capturing an image of something dim.
In the DSLR implementation there is a RAW image output, but typically it is not completely RAW. Some evidence of noise reduction and hot pixel removal is still visible on close inspection. This can have a negative effect on the image for astronomy such as the “star eater” effect. However, QHY Cameras offer TRUE RAW IMAGE OUTPUT and produces an image comprised of the original signal only, thereby maintaining the maximum flexibility for post-acquisition astronomical image processing programs and other scientific imaging applications.
Based on almost 20-year cooled camera design experience, The QHY cooled camera has implemented the fully dew control solutions. The optic window has built-in dew heater and the chamber is protected from internal humidity condensation. An electric heating board for the chamber window can prevent the formation of dew and the sensor itself is kept dry with our silicon gel tube socket design for control of humidity within the sensor chamber.
In addition to dual stage TE cooling, QHYCCD implements proprietary technology in hardware to control the dark current noise.
|COMS Sensor||SONY IMX492 （MONO）|
(QHY294C Discontinued in 2022)
|Effective Pixel Area||4164*2796|
46.8MP（Extended Pixel Mode）
|Sensor Size||4/3 inch
|AD Sample Depth||14bit|
|Full Frame Rate||Standard 11.6mega pixel mode
“Unlock” 47mega pixel mode
8340*5644 4FPS@14BIT and 8BIT
*Note：QHYCCD has optimized the cmos drive freqency and limit the max frame rate. The CMOS sensor may not work under the maxium frequency to ensure the better noise performance. If you need the customized higher frame rate version please contact QHYCCD.
|Readout Noise||1.6-1.2e- High gain mode
6.9-5.2e- Low gain mode
|Dark Current||0.002e/pixel/sec @-20C
|Exposure Time Range||60us-3600sec|
|Unity Gain||1600 (11MP Mode)
2600 (47MP Mode)
|Hardware Anti-Glow Reduction||Yes. Can reduce the amp glow of the sensor in long exposure.|
|Shutter Type||Electric Rolling Shutter|
|Built-in Image Buffer||256MByte DDR3 Memory|
|Cooling System||Dual Stage TEC cooler（about -35C below ambient）|
|Optic Window Type||AR+AR High Quality Multi-Layer Anti-Reflection Coating|
|Back Focal Length||17.5mm|
For cameras with a sensor larger than 1-inch and smaller than APS-C (QHY163m/294m) we recommend a combination of CFW3M (US) + OAGM (optional);
|Model||BFL Consumed||Filters Supported|
Back Focal Length (BFL), in the commercial camera field, refers to the design distance from the center of the rear lens element to the surface of the sensor. Generally, the lens will only focus correctly at infinity if the camera’s back focal length meets the standard requirements provided by the lens manufacturer. This is also true for many Multi-Purpose Coma Correctors designed to be used on telescopes before the camera.
|Optical system||Back focal length required|
|Typical Multi-Purpose Coma Corrector||55mm – 57.5mm|
|Canon 35mm lens||44.1mm|
|Nikon 35mm lens||46.5mm|
The camera requires an input voltage between 11V and 13.8V. If the input voltage is too low the camera will stop functioning or it may reboot when the TEC power percent is high, causing a drain on the power. Therefore, please make sure the input voltage arrived to the camera is adequate. 12V is the best but please note that a 12V cable that is very long or a cable with small conductor wire may exhibit enough resistance to cause a voltage drop between the power supply and the camera. The formular is: V(drop) = I * R (cable). It is advised that a very long 12V power cable not be used. It is better to place the 12V AC adapter closer to the camera.
First connect the 12V power supply, then connect the camera to your computer via the USB3.0 cable. Make sure the camera is plugged in before connecting the camera to the computer, otherwise the camera will not be recognized. When you connect the camera for the first time, the system discovers the new device and looks for drivers for it. You can skip the online search step by clicking “Skip obtaining the driver software from Windows Update” and the computer will automatically find the driver locally and install it. If we take the 5IIISeries driver as an example (shown below), after the driver software is successfully installed, you will see QHY5IIISeries_IO in the device manager.
Please note that the input voltage cannot be lower than 11.5v, otherwise the device will be unable to work normally.
All-in-one Pack supports most QHYCCD models only except PoleMaster and several discontinued CCD cameras.
Download Page: https://www.qhyccd.com/download/
Video Tutorial: https://www.youtube.com/embed/mZDxIK0GZRc?start=1
Before using software, make sure you have connected the cooling camera to the 12V power supply and connected it to the computer with a USB3.0 data cable. If it’s an uncooled camera, 12V power is not needed. We recommend 64-bit Software, like SharpCAP x64 , N.I.N.A x64. etc., especially when you’re using 16bit cameras.
In NINA, you can select the device to connect to QHY Camera directly without ASCOM driver.
If connecting to the camera via ASCOM is desired, first make sure you have installed both the QHYCCD ASCOM Drivers and ASCOM Platform. Then you would select the appropriate camera driver under the ASCOM section. Then click the Connect icon. Here we take NINA as an example, but it’s similar to other software packages supporting ASCOM, like MaxDL, The SkyX, etc.
Launch SharpCap. If the software and drivers mentioned above are installed successfully, the video image will appear automatically about 3 seconds after the software loads. You will also see the frame rate in the lower left corner of the software window as shown below.
If you have already started the SharpCap software before connecting the camera, in order to open the camera, click on the “camera” in the menu bar and then select the device.
Offset adjustment. When you completely block the camera (i.e., like taking a dark frame) you may find that the image is not really zero. Sometimes this will reduce the quality of the image contrast. You can get a better dark field by adjusting the offset. You can confirm this by opening the histogram as indicated in the figure below.
If you want to enter the 16-bit image mode, select the “RAW16” mode.
By selecting the “LX” mode you can expand the exposure setting range and take long exposures.
After cooling devices connected to the 12V power supply, the temperature control circuit will be activated. You can control the CMOS temperature by adjusting the settings in the figure below. Basically, you can control the temperature of CMOS by either adjusting “Cooler Power” or clicking “Auto” and setting “Target Temperature”. You can also see the CMOS temperature at the lower-left corner of the software window.
Now the FAQ part has been intergrated into “QHYCCD Help Center“–Knowledge base
This is QHYCCD Help Center. Here you can:
Submit a Ticket: Describe the issue you met while you’re using them. Our technicans will reply you in 48 hours during working days. You don’t have to check the Ticket update everyday—they can receive email notifications and know if there’s any update.
Knowledge Base: Here lists some tips for using your gears, or solutions to issues that you may met. Help your self!
Support History: Check your ticket’s status.
There is a hole in the side of the camera near the front plate that is normally plugged by a screw with an o-ring. If there’s moisture in the CMOS chamber that causes fog, you can connect the desiccant tube to this hole for drying. There would better be some cotton inside to prevent the desiccants from entering the CMOS chamber.
Please note that you may need to prepare desiccants yourself, because for most countries and regions desiccants are prohibited by air transport. Since QHY always deliver your goods by air, sorry that we can’t provide desiccants for you directly.
If you find dust on the CMOS sensor, you can first unscrew the front plate of the cam and then clean the CMOS sensor with a cleaning kit for SLR camera sensors. Because the CMOS sensor has an AR (or AR/IR) coating, you need to be careful when cleaning. This coating can scratch easily so you should not use excessive force when cleaning dust from its surface.
All QHY cooling cameras have built-in heating plates to prevent fogging. However, If the ambient humidity is very high, the optical window of the CMOS chamber may have condensation issues. Then try the following:
1. Avoid directing the camera towards the ground. The density of cold air is greater than of hot air. If the camera is facing down, cold air will be more accessible to the glass, causing it to cool down and fog.
2. Slightly increase the temperature of the CMOS sensor .
3. Check if the heating plate is normally working. If the heating plate is not working, the glass will be very easy to fog, the temperature of the heating plate can reach 65-70 °C in the environment of 25 °C. If it does not reach this, the heating plate may be damaged. Please contact us for maintenance.
Please avoid thermal shock during use. Thermal shock refers to the internal stress that the TE cooler has to withstand due to the thermal expansion and contraction when the temperature of the TEC suddenly rises or falls. Thermal shock may shorten the life of the TEC or even damage it.
Therefore, when you start using the TEC to adjust the CMOS temperature, you should gradually increase the TEC power rather than turning the TEC to maximum power. If the power of the TEC is high before disconnecting the power supply, you should also gradually reduce the power of the TEC and then disconnect the power supply.
For beginner, we recommend that you set the gain to “unit-gain”. Unit-gain is the gain when system gain is 1 (1e/ADU). This number is shown in the table above, like the unit-gain of QHY168C is 10. In fact, increasing or decreasing a bit doesn’t make a big difference.
You could increase or decrease Gain according to the condition. For example, if your optical system is fast, like F2.2 to F5, or long exposure for more than 5 minutes without narrowband filters, then you can decrease GAIN to achieve a higher dynamic range and make better use of full well capacity. By doing so you can avoid overexposure.
If you use narrowband filter on a slow optical system like F6 to F10, or short exposure time, the amount of photons received will be less. In this case you can increase GAIN to make better use of characteristics of low read-out noise in high GAIN value.
There is no fixed “best value” for OFFSET. To set OFFSET, you should take the bias frame and dark frame at a certain GAIN value, then check the histogram of the frames.
The histogram distribution is a peak-like curve. While changing the OFFSET value, the histogram will move left or right. We need to guarantee the range of the whole curve won’t be chopped off at the end. At the same time, we need to keep a little residue on the left side, just over 0 a bit.
Pay attention that under different GAIN values, the width of this peak varies. The higher the GAIN is, the wider the distribution will be. So OFFSET value at low GAIN is not suitable for high GAIN because the curve is easily to be chopped off.
For those CMOS less than native 16-bits, the AD sampling accuracy doesn’t match perfectly with the full well capacity. At low GAIN level, the system gain will be couple electrons per ADU. The camera loses the ability to distinguish the strength of the signal because of such sampling error.
When GAIN increases, the system gain will decrease. However, increasing GAIN will limit the full charge of the well. If the system gain is 1 for a 12bit CMOS camera, the pixel will be saturated at only 4096 electrons (full well). Some bright stars will be easily saturated. This problem goes worse under fast optical system or long exposure. Over saturated objects cannot be fixed during post processing (unless you shrink stars, like in PixInsight). Also, the color saturation of the star will be affected. As result, the stars will be huge and white washed. We should decrease the gain value in this case, to gain a higher full well capacity.
Under long exposure or using fast optical system, the pixel will receive more photons. The variation of quantized noise from the photon which you can consider as natural dithering of the light intensity, will be greater than the “noise” from the sampling error. Therefore, the effect of the sampling error will diminish. By averaging multiple exposures, this will compensate the lack of depth of the picture because of the sampling error.
If the number of received photons is limited, like using narrowband filters or short exposures, we can increase the GAIN value. It is because the stars will not be easily saturated. At the same time, we limit the noise from the background cosmic radiation. Under this condition, the readout noise and quantized noise are the major factors that affect the ability to distinguish dim light or objects. By increasing the GAIN value in order to decrease the readout noise and quantized noise from sampling error, this would greatly increase the signal to noise ratio.
|Cooled CMOS Camera||Bayer|
|Cooled CCD Camera||Bayer|
|Planetary and Guiding||Bayer|
Now the ratio R”:G”=(R+bias)/(2R+bias) and it is not equ to 1:2. It shows the bias will effect the true value of the R:G. And the ratio of R:G will arious when the image light changed. It is hardly to correct with a fixed ratio.
But for DSO capture, You should keep the offset above zero and avoid the background is cut off. A background from 1000-5000 is a good value(16bit mode) for DSO imaging.