QHY10 – an afterparty „review“
OK, it’s not going to be a real review, but just a bunch of user comments after using this camera for a while. First, I’d like to state the reasons why did I purchase it? I wanted a camera that is color (OSC, one shot color) because I own only couple of mono cameras. I wanted to experience ADC settings on my own and test its impact on real noise characteristics (readout noise etc.). I wanted the color version for constellation photography and for comet imaging (do rarely, but some day it could be handy). In time-limited imaging sessions (like on a vacation – once per year) it’s good to collect the same amount of data over all three color filters (Red, Green and Blue). With mono I have many times ended missing one of the three channels (because for best results you always have to refocus between filters no matter how parfocal they are so you can’t shoot R/G/B/R/G/B sequence). So my vision was to use the camera once per year (or few times) on a vacation to shoot color images in places with as low light pollution as possible (it turned out to be hard to find these skies on a family vacation, therefore next time I plan shooting narrow band only) on say Astrotrac platform (that only allows for 2 hours of tracking without rewind and reworking the composition of the image – with AZ head it’s easy to re-composite, you only have to rewind the RA (azimuth) axis). The initial vision was to use a field-power box (LiPO battery pack) with limited capacity in order to be low-weight due to portability reasons.
This is strictly a person subjective sum of points from a most demanding astro-imager on the planet Earth. Your experience will most probably differ to mine.
Here are the weak points:
low light sensitivity. I find the camera rather light insensitive. If you compare it with simple DSLR like Canon set on ISO 800 then you get much dimmer image with QHY10. The reason is OK and clear to me – with QHY10′s ADC settings on gain/offset combination to a reasonable number (in order to maintain as much dynamic range as possible – in order to dig out the image out of it) you barely see the image you are shooting – this makes doing composition very difficult without computer aid. The chip is SuperHAD “only”, not high QE like in ExView HAD chips.
on top of the previous issue – the camera driver (at least in MaxIm DL/ASCOM driver) downloads the image both vertically flipped and vertically larger (image has dimension of 2612×3896 instead of 3896×2612 as one would like to have – my laptop screen is wide, not tall) which really makes the composition uneasy.
two-frame readout mode (no progressive scan readout) which is maybe even worse than interlined readout (which in fact, without mechanical shutter makes things even more complicated – but on the other side what’s missing can’t get broken ). The problem is that you really need to take good set of bias frame in order to calibrate e.g. flat field calibration frames to remove the color gradient that appears in the image if you do not calibrate well your raw light data.
previous issue leads to another problem – hot pixels – no way how to effectively use bad pixel maps and bias-only calibration. Therefore best works to take dark frames as the only (and flat fields, of course) calibration data (no biases, no BPM). The darks fixes both hotpixels (as well as dithering would fix) and color gradient in image from two-frame readout mode (and some visible luminescence in the corners too).
it’s really not easy to take good flat field calibration frame so as all three color channels are reasonably lit (having min and max ADU values in dark corners and bright center of the image on reasonable numbers – like from 10 000 ADU to 30 000 ADU). This is doable and fixable with e.g. “soft” LPS-P2 filter, but with stronger UHC/CLS/LPS-V4 you can’t get good values for Blue (or Green) channel.
post processing seems to me to take even much more work than simple mono camera. Because of this experience I have learned how to write scripts for automation for MaxIm DL (to extract Bayer matrix – color planes, to “convert color” and to “split tricolor” etc.).
focusing – I really do not have super apochromatic optics so I essentially have to choose if I well-focus green or blue or red only. Even using Bahtinov mask did not help much. I found out that test short subs for focus check works best (measuring FWHM in the image after 30-45 seconds). Lower resolution (in terms of detail in the image) of OSC color cameras versus mono is a well known fact. But I like to double check the well known myths and fairy tales and hearsay rumor myself.
the best is to shoot 15min subframes (Lights) or even longer which doesn’t match my intended Astrotrac travel approach.
I hate the short power cable and DC-201 unit external box approach (it’s ineffective/not economical to convert from 12V stable to 18V and vice versa). Too many cables to worry about. And if something gets wrong you need to unplug everything in correct order (reverse than plugging) and for safety reboot your computer and plug everything again together in correct order (check your user’s manual!).
cooling regulation for small deltas tends to overshoot and takes much time to settle down. Do not like the TEC protection option as sometimes I have to charge my battery by starting up the engine of my car which puts the voltage up to 14V. Safe and best approach is to use 12V/4A stabilized power supply in all cases.
my personal suspect that the camera’s front cover window (optical window) is not fully multicoated and therefore causes reflections around brighter stars.
my particular camera had really well aligned (square) CCD chip surface with camera’s head (attachment threads)
the cooling on MAX was fast and with very high delta on ambient temperature
my camera never dew up (cooling at -20 C) while other without effective front window heater did on the same night
camera was completely meeting manufacturer’s specification in all terms (noise etc.)
large full well capacity of pixels (over 40.000 e-) suitable for both a fast astrograph and for shooting longer subs (15 – 20 min subs) without burning out the color of stars
large 28mm diagonal CCD chip surface (this can also be a negative because you need a perfect optics to make a full use of it – and when you have such optics then why not to get a full frame (36x24mm) chip instead?)
surprisingly the camera drivers installed on first attempt without problems
nice and compact camera in a round body
Here are some strong points:
Why did I sell it? [new was for 2.400 EUR, sold my tested and proven for 1.520 EUR!]. It did not meet my expectation and the reasons why I purchased it. Now I have switched to Sony ICX694 (new generation ExView HAD II) chip-equipped mono CCD camera. I prefer high sensitivity and low noise with much smaller FOV (but insanely nice narrow band capabilities) than large (and color), but dim picture to complement my large format camera. For large FOV I will keep my MII G3-11000 CCD (mono, of course) because that’s the best (and cheapest) camera with the damn noisy KAI-11002ME CCD for an European citizen at the moment.
Related QHY articles:
Set-Point TEC Cooling Tests of QHY CCD camera
QHY10 – Binning, Gain, Offset, Noise, Light Response etc.
To complete my complaints monolog, I should show some of my images done with this CCD camera:
Pavel Pech, QHY10 OSC CCD
QHY10 two frame readout mode
QHY10 single and master bias frame
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