QHY10 Shipped to UK

1. 

   Rated 5 out of 5

   Alan Clitherow – 13th October 2015

   A quick review of the QHY10 One Shot Colour cooled CCD camera.
   In one sentence? I think this is a very under-rated camera.
   I have had a number of astronomical cameras including early QHY models and the excellent Atik 314L, a small chipped but sensitive monochrome camera. I wanted to move to a larger chipped camera that would allow me to capitalize on small windows of good weather to capture all the RGB data in one go, over a large field and without having to spread the capture of data over several nights. For the budget conscious the obvious answer is an astro-modified DSLR but my experience of these is that coping with the noise of longer exposures is difficult and the relative cheapness does not outweigh the benefits of a cooled CCD camera. I did have a disastrous flirtation with a highly modified deep-cooled DSLR camera which held much promise but, ultimately was unreliable and was wasted money.
   So, what about the QHY10? It has an APS-C sized Sony ICX493 chip with square 6.05μ pixels and a full well depth of around 46 thousand electron volts. This means it has a large field of view and can capture faint detail in long exposures without totally blowing-out (over exposing) bright areas or most faint stars. You still capture star colour with it when other chips with shallower well-depths would fully saturate the stars. Side by side exposures with the QHY10 and a DSLR will have the raw image from the DSLR look brighter but this is not due to poor sensitivity in the QHY10, rather it is due to the much shallower well-depth of the average DSLR. The pixels have collected as much light but the well is fuller so the picture looks brighter. The QHY10 will have captured at least as many photons but the well is no-where near full so the raw image is darker. Stretching the image to brighten them will reveal as much or more detail from the QHY10, with less noise (deep-cooled chip) and better star colour due to lack of saturation of bright areas on the chip. Well, that’s my experience of the camera.
   In practical terms the camera drivers and capture software installed with no problems on my rather old Windows XP laptop. You can use the camera with third party capture software but I use the program supplied by QHY which is a little quirky but stable and fully functional. You select the connected camera from a drop-down window of available cameras, then open the camera-settings window to turn on and set the regulated cooling temperature for the chip.
   I generally use -20 degrees C and the camera stabilizes at that temperature in less than 5 minutes and remains within a couple of degrees of it throughout my imaging sessions. Note that is an actual temperature, not 20 degrees below ambient. This stable temperature lets me take libraries of dark-frames for various exposure times rather than having to shoot new dark-frames for each set of light-frames; a great time saver. You can cool to well below -20, I think the absolute minimum is -45 but I don’t think that would be achievable on a warm evening and, in any case, I didn’t see much improvement in dark-noise with temperatures below -20 degrees C.
   The camera lets you take a ‘live-view’ that is a succession of preview images to help with locating your target and you can use 2 by 2 binning to increase sensitivity while doing this. Alternatively you can apply varying levels of screen stretch to the captured image to bring up faint detail along with auto adjustment of the black and white points; all of this helps you frame faint targets without having to do minute long exposures to find them. The auto and screen-stretch functions do not affect any saved images, only the way they appear on the capture screen.
   One quirk of QHY cameras that I wasn’t used to was the correct setting of the gain and offset sliders in the preview and capture sections of the camera control software. Bernard, from Modern Astronomy, provided a ‘cheat-sheet’ with the camera giving suggested settings for these sliders and they work well. The software also has an effective focussing aid which works by putting a box around a non-saturated star and looking at peak brightness levels and FWHM size of the airy-disc of this star; this was very effective with short-focal length telescopes and some camera lenses which can be hard to focus exactly.
   Once this is done you can set the camera to take a series of images at whatever exposure length you want, just remember to de-select the ‘fast download’ box in the exposure-capture setting to get the best quality images. The software saves in 16 bit FITS format (uncompressed data) ‘though, for some reason, the image is presented and saved in portrait rather than landscape format and with a black edge to one side that needs cropping off in post processing.
   I find the freeware stacking software DeepSkyStacker works well with the FITS files from this camera and produces a clean image for importation into PhotoShop or whatever is your preferred processing software. Overall I found the camera no trouble to install or use, it is sensitive and capable of imaging faint deep sky objects if you have a well guided mount. Cooling levels are deep and stable with low levels of dark noise; images of more than 20 minutes duration each are not a problem. I suspect it has a higher quantum-efficiency than the average DSLR camera, if only because of figures given for the Sony CCD chip versus the average values for astro-modified DSLR cameras, and its deep well depth helps with reduced saturation and better colours for faint stars.
   I bought the camera as a step-up from a modified DSLR camera and, for me, it has worked very well. I can take 6 by 10 minute exposures in a limited viewing window in the weather, stack the results and have a usable image with low noise and plenty of detail, something I wasn’t able to achieve with a non-cooled DSLR. You don’t see many of these cameras about, which is a shame because they are, I think, very under rated.
   Alan Clitherow.

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