QHY8 One Shot Colour Cooled Camera
Submitted: Wednesday, 11th June 2008 by Clive
A number of considerations were taken prior to the purchase. I had been using a 6 megapixel modified Canon digital camera for a while, and liked the size of the image and didn’t want to go to a smaller size. Noise on warmer nights had been an issue, and just the ability to do a lengthy exposure. I had stuck with 360-second exposures for most imaging. There was also the SLOW download times for setting up the frame and testing focus, and finally I had to stand with a stopwatch to time each of my exposures. So was there a better alternative that wasn’t going to break the bank.
People who had recently purchased a QHY8 were PM’d with “ what do you think. Is it any good”, as it had only recently been used the answer was I’m still working on it. Further postings on IceInSpace saw a consensus of opinions that this was a camera to own…… So I bought one.
Arrival of Camera
End of April and a smallish cardboard box marked FRAGILE arrive at the Post Office, this is it.
Returning home the contents were placed upon the kitchen table, all items ordered had arrived good condition:
An optional filter/neck is a clear version which allows for InfraRed or Ultra Violet Imaging with appropriate filtration (didn’t order this).
The first thing to do was open up the instruction disk and check the contents, as per the text file, the recommended drivers were installed. Following what was a clear and simple document (including pictures) the camera was put together with all the required cables, fairly straight-forward and well documented, on the computer its to be used with (running XP) it was recognized instantly and we are ready to go. It made a nice change not having to hunt all over the net trying to find a solution for a conflict.
The package came with a program for taking the image and drivers for other software, although the program recognized the camera, there was no documentation on how to use the program (apparently the drivers had been updated and the program manual had been omitted as it possibly needed updating). Some enquiries were made with the Australian supplier who provided basic information and a commitment to provide some documentation on his website. Now available online here.
Running the program and with a basic grip on some issues, I let the camera run, while I assessed the various functions of the imaging program.
The camera has cooling to its chip, reputed to be 45 degrees C below ambient. It was not measured so presume it to be correct. There is also a small high speed fan at the rear of the camera body which showed no evident vibration. One thing some are going to find a problem is that of condensation on the outside of the first filter, because it's co cold inside the camera it passes on some of that to the front filter, the inside has remained clear but when another attachment is applied the moisture in the trapped air condensed on the front of the supplied UV/IR filter, it also condensed when no further filters were applied. It is interesting to note that when a Baader MPCC was only used I noticed no condensation perhaps as glass was thicker it would be a longer time to cool or between lenses is dry or a vacuum? Can’t say for sure.
There are a couple of solutions - You can either remove all the moisture from between filters Via a silica Gel moisture absorption, I put it all in a sealed plastic bag and watched the humidity drop and then reassemble in the bag….. It worked to a point but you have to pretty much get it ALL out. I did toy with the idea of assembling it in a large walk in freezer as once temp is low enough the moisture freezes out and the air is dry….. never tried it, maybe it works? In the end I just attached a 2 inch Dewheater strip around the tube and left it on, it worked well enough to become the way I will use it in the future (see picture below).
Below are specifications provided at the distributors website :
Time for a bit of real world testing. Plug in camera and associated equipment, open capture program and away we go.
This was the first time I had done an image with the QHY8 so I set it for an initial run of 10 x 600 seconds, adjusted focus just using the preview function, I could have used the focus section but found I could adjust well enough as it was, and this was just a test run to see the cameras response. Auto guiding was set up, and away it went. It was a very dewy night and I decided to leave it all alone and go into a warm house.
A bit over an hour later, up to the observatory to check the results. At this point I got somewhat of a surprise/shock having done only DSLR exposures previously, I expected a similar image only cleaner. That’s not exactly how it happened.
When using a DSLR I typically exposed for 6 minutes at ISO 800, shooting at this would typically fill the pixel wells with a bright object such as Eta Carinae, so a bright image would be displayed. Using the QHY8 I estimate it would take about 5 times as long to fill the pixel wells to that same brightness on the display screen (note brightness does not equate to bit depth or detail), HOWEVER the QHY8 has a far greater Bit depth than the old camera I had been using, 16 times to be precise, so the long and short of it is although the image APPEARS dark it actually has more detail, and once a stretch is applied more can be done. An added benefit is that if you want to do really long exposures and collect a few more photons for that faint detail, you can.
I hope that makes sense.
The processing really lies outside of the parameters of this brief report, but a brief summary would be thus.
1. Calibrate 2. Debayer 3.Stack 4.Stretch 5.Color Balance …… tinker as you will.
The image below has NO dark frames applied NO flat fields (could have used a flat field though). Total exposure time was only an hour as it was meant to be a test with settings: Gain 50 Offset 118 10 x 600 sec.
All in all at the price the software issue is easily covered and still remains a bargain, so would I buy it again?
This camera would have to be what you would consider a bargain; finally the CCD market has come to a price available to many imagers. This is probably where I add the disclaimer that I have nothing to do with the retailer of these cameras, and well I guess that’s about it, hopefully this will give someone interested in the camera some ideas, and those who have purchased it some of the fundamentals of its working.
Review by Clive (Alchemy). Discuss this review on the IceInSpace Forum.