Manufacturer's LinkUSA Distributor LinkI have been seriously Astroimaging for about 5 years now and up until May of 2010 with Canon DSLR’s. I thoroughly enjoy every aspect of this wonderful addiction except imaging during the summer months. The high ambient temperatures at night cause the thermal signal to rise high enough in to the wanted signal, that it becomes difficult to attain an decent signal to noise ratio (S/N). I accepted this for what it was up until this summer when I said “enough is enough, I want a cooled CCD” and sold all of my DSLR gear and placed my order for the QHY9-C One Shot Color (OSC) CCD Camera. This camera is based on the very popular full frame CCD chip by Kodak the KAF-8300CE. It is a 4/3 format CCD with 5.4 micron square pixels in a 17.96 mm X 13.52 mm 8.3 MP array. The chip features 1000X anti-blooming protection as well as microlensing to improve quantum efficiency.
I chose the QHY9-C package due to a few strong points that I saw over the competition. Firstly was the price point, it is about $300-500 below its nearest competitors and offers features that the others do not. For instance, it can regulate cooling within 0.1°C down to -50°C absolute temperature. It also has a 32MB onboard memory buffer which allows the camera to read the chip into memory and then transfer that memory to the PC, reducing the chance of transfer noise bleeding into the signal. Secondly, the camera’s software drivers are being developed in an open source format and are based on the ASCOM standard for ease of use and compatibility. This was a big plus in my mind being that I am a professional software developer and fully understand how long a new release can take under a large corporate control system. Lastly is the excellent support received in the QHY Forums. Dr Q and others are quick to respond and truly want to correct anything as fast as possible.
The CCD-Labs package comes with the following:
1. DC201 power module/TEC controller. This takes 12VDC as an input and supplies the 3 voltages that the cameras needs as well as the pulse width modulated TEC signals to the camera. This is all done over a single, multi conductor shielded cable. Data transfer and computer control is accomplished over a standard USB 2.0 interface.
2. Also in the package was a 4A AC-DC 12V power supply, cigarettes lighter style power cable for use with a battery and a desiccant plug that comes mounted to the camera to keep everything dry.
3. It all came shipped in a nice Pelican 1200 air tight case. Part of the service that CCD-Labs offer, at no additional cost over the manufacturer’s list price, is purging the CCD chamber with Argon to ensure frost free imaging, installation of the desiccant plug and full testing.
4. A CD with the latest drivers a licensed copy of Nebulosity 2.0 and documentation (really lacking at the time I purchased mine) was included as well as an initial start-up procedure.
Prior to the CCD arriving I had downloaded and installed the latest set of ASCOM based drivers and tested it out as much as possible with MaximDL so that when the CCD arrived I would be ready to go. After much anticipation, FedEx delivered a package in the Pelican Case OEM box. Inside the cardboard was the Pelican 1200 case with all of the parts, nicely placed in the plucked foam. The DC201, CCD and all cables fit nicely inside the case. It took me a minute to find the CD and start-up instructions as they were hiding behind the foam in the case lid.
My first impression of the camera was quite positive, the fit and finish are decent, not quite that of the more expensive models, but they had to get cost down somewhere. The camera is real light and small. It weighs only 510 grams (1.12lbs) and slightly smaller around than a CD. There is a power connector next to the USB connector and a SMA connector to deliver power to a filter wheel. There is a 2 inch nose piece fitted with a Anti Reflective window that presents T-Threads to attach the camera to your equipment.
The first thing that has to be done with this CCD prior to imaging is to set the Gain and Offset values for the ADC circuitry. I use MaximDL for camera control and used it to set the Offset and Gain. Most other manufacturers hardcode this in their drivers, but, QHY decided to expose these parameters which I like. Small changes in these values have a profound impact on the signal quality and they need to be set properly. I followed a simple procedure and had them set in no time. You take a bias shot, with the gain at 0, and increase the offset until your background average is about 800 ADUs. You then expose the camera to daylight and adjust the gain until your maximum value falls short of 65536 ADUs (maximum possible for a 16 bit ADC). I set mine up to hit about 60K ADUs to keep the data out of the non-linear area of the CCD. Once these are set you leave them alone and you are ready to image. Before you start this you have to let the CCD reach a stable temperature. I did my calibration at -20°C as that is what I plan on imaging with. I told MaximDL to enable the Two Stage Regulated TEC and configured the set point for -20°C. The driver reported that it reached temperature within 2 minutes. I read that it is good practice to allow an additional 10 minutes after the reported temperature reaches the set-point. This is due to the fact that the temperature sensor is not physically on the chip; it is on a copper pad next to the chip. No real issue here as there is plenty to do while you are waiting anyway.
I only had to wait a few agonizing days from when I received it until I was able to shoot something with it. I started with M13 with no filters to see how the data would look directly from the camera. I found that 100 seconds unfiltered was good so I gave that a try. On the slowest readout speed (the slower the cleaner the signal is) the full frame was stored on my hard drive in under 20 seconds. The driver does support a fast readout mode and partial readout to allow for fast focusing. With a box drawn around a star I was getting updated focus frames every 0.5 seconds. This is perfect for focusing with a Bahtinov Mask.
Dark and bias calibration frames are taken the same way as with a DSLR so that was no issue at all. Flats, on the other hand, needed some figuring. You want to expose your flats at about 20K~25K ADUs while keeping the exposure time greater than 0.5 seconds. The chip is capable of a minimum exposure time of ~0.002 seconds, but, the shutter speed is the limiting factor. Anything faster than 0.5 seconds will leave a shadow on the CCD as the shutter moves across the chip. I tried 0.5 second exposures and my light box saturated the chip, I tried adding another sheet of white Plexiglas and 2 T shirts and was able to get a somewhat decent flat that way. I have since added a variable DCDC converter to my light box so I can drop the voltage to the 12V bulbs to match my set-up. No issues with flats anymore. With the LPS filter I took 4 second exposures with the light box at 7.5VDC. With the 7nm Ha filter I took 6 second exposures with the light box at 12VDC.
The camera’s thermal signal is so low it is not a factor, but dark frames are necessary to remove hot/cold pixels. You could get away with bias + bad pixel mapping but I cannot figure out how to have the bad pixel map applied without dark calibrating….something for a later date!
I have enjoyed 3 sessions with this camera so far and have had no issues at all. Nothing mechanical or electrical has come up and the software has performed flawlessly. Overall I more pleased with this camera than I thought I would be for the price. The color rendition is great and narrowband (I have only tried Ha at the time I wrote this) was better than I expected it to be.
If you are considering an OSC CCD I would strongly encourage you to perform your own research, but please take a serious look at the QHY9-C because its performance demands at least that!
The three images below are my 1st, 2nd and 3rd sessions respectively
M13, 9*100 seconds, no filters, poorly calibrated
M13, 37* 240 seconds, IDAS LPS-V3, dark, flat, bias and pixel mapped
NGC6888, 9*1200 seconds, Baader 7nm Ha filter, dark, flat, bias and pixel mapped
I hope this review was informative and will help you reach your decision!
Clear Skies!
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