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
By Christopher Go, QHY5III485C
QHY5III485C uses Sony’s new IMX485, back-illuminated, 8.4 megapixel color CMOS sensor with an array of 3864 x 2180 pixels at 2.9um. With USB 3.0 interface, the full frame rate of 44 FPS at 8-bits or 18.5 FPS at 16-bits. Smaller regions of interest will yield even faster frame rates.
The resolution of QHY5III485C is 16:9, which is equivalent to the mainstream video output ratio. With the native high resolution, 485C can play a special role in recording astronomical video and astronomical science live broadcast.
QHY5III485C is specially equipped with 128MB DDR bulid-in image buffer. In non-video output mode, DDR built-in buffer can effectively relieve the transmission pressure brought by high-resolution large data volume and reduce information loss.
One benefit of the back-illuminated CMOS structure is improved sensitivity. 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.
|CMOS Sensor||Sony IMX485|
|Frame Rate @Full Frame||44FPS@8-bits|
|Frame rate @ROI readout||78.5FPS@1200lines, 87FPS@1080lines, 91.5FPS@1024lines, 97.5FPS@960lines, 121FPS@768lines, 190FPS@480lines|
|Ful Well Capacity||12ke-|
|A/D||12bit (output as 16bit and 8bit)|
|Non-volatile memory / On camera storage||128MB DDR II Memory Buffer|
|Telescope Interface||1.25-inch, CS mount|
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
Here we mainly take QHY5III462C as example. This User Guide can be applied to all QHY5III series Camera.
Adjust OFFSET. You will find that when the lens cover is closed and the image is completely black, the background of the image is still not completely black. Therefore, you need to adjust the OFFSET value to make the image darker. Generally speaking, for planetary shooting, setting the image background to very dark is not a big problem. For deep space shooting, a certain background should be retained, and it should not be completely black, otherwise it will lead to the loss of a weak background cloud.
There are many astronomical software support ASCOM, you can connect QHY5III462C through ASCOM. Note that currently QHY5III462C only supports the ordinary ASCOM shooting mode, and does not yet support the ASCOM video mode. In order to obtain the maximum dynamic range and effect, the ASCOM driver uses the maximum number of digits transmission by default (for QHY5III462C, 12-bit), the image is stored in a 16-bit format, and the lower bits are filled with zeros.
Use MAXIMDL for Plantery Imaging
Using PHD for Guiding
Select a star point on the screen, a green frame appears, and then select to start calibrating the equatorial mount and guide star.
QHYCCD BroadCast WDM Camera is a broadcast driver that supports QHYCCD cameras with video broadcast function, which can meet the needs of customers to send video images to other target software. For example, use sharpcap to connect a WDM-enabled camera, and the sharpcap display video image can be sent to other WDM-supported software for display, which is suitable for video online broadcast applications.
The installation process is over, right-click the computer to find the device manager, and check that the image device name is QHYCCD BroadCast WDM Camera, which means the installation is successful.
QHY5III Guiding Line Sequence Definition
The guide circuit contains an optocoupler isolator. The COMMON pin is generally connected to GND. Usually the four direction pins from the equatorial mount are internally pulled up on the equatorial mount circuit, so when the QHY5III sends out the guide star pulse, the optocoupler pulls it down to realize the output of the guide star command.
The line sequence of the socket at the equatorial mount is
If you use other types of equatorial mounts, please confirm whether the wire sequence is the same as the above.
Because QHY5III series cameras have a very high frame rate and data volume, not all computers can reach the maximum frame rate. Generally I7 quad-core is no problem. However, the CPU occupancy rate will also affect the maximum frame rate, so when using QHY5III, try to close other programs that occupy the CPU and free up the CPU to process the data. If the CPU usage is too high, the program will respond slowly or even crash.
|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.