QHY’s 533C color camera now has a monochromatic cousin: the QHY533M. This backside-illuminated camera has a small sensor – only 11.3mm to each square side – but it packs a punch in sensitivity and image quality. With 3.76 µm pixels, it is well-suited for short-focal-length refractors and camera lenses. Its small sensor size leaves out coma, curvature, and other effects, and can be used with 1.25” filters, making it a good starting point for beginners ready to make the jump to monochrome and experienced imagers looking for a more sensitive, updated camera without dealing with enormous files.
The test kit I received from QHY included their 1.25” QHYCFW3 filter wheel, several spacers, a 1.25” nosepiece, a USB 3.0 camera cable, USB 2.0 and serial filter wheel cables, and a 12V power supply with a screw-on connector. Connecting the filter wheel to the camera via the included serial cable saves an additional USB cable running down to the USB hub.
The camera body is enormous compared to the size of the sensor! It was somewhat comical.
The body is well-constructed and feels solid. It’s a bit on the heavy side (845g, or 1 lb 13 oz – about 5 oz heavier than the ZWO ASI2600MC Pro), but workable. On the bottom of the camera body is a foot with a standard ¼-20 connection to attach to a tripod or mounting plate, which is useful for connecting to camera lenses. The front plate can be rotated so that the chip is square with the orientation of the rest of the optics train.
I had to install the beta driver for the moment for this camera, but I was able to open the camera in SharpCap without much trouble using the USB 3.0 cable on a USB 3.0 port. The camera must be connected to the 12V power to operate. The filter wheel is very quiet – I had to put my hand on it to make sure it was actually working.
Using the Camera
The first thing I noted when running an imaging sequence was how quickly the camera cooled. My cameras from ZWO ramp up the cooler power slowly, taking about 6 minutes to cool 25C, while the QHY ramps to 100% until it reaches the set temperature, taking only 3 minutes or less. That may be a small difference, but it is really nice to be able to cool quickly, especially when recovering a sequence after an issue or pausing it to switch programs for planetary imaging, focusing, etc.
I did, however, run into a few problems. It does not work on USB 2.0 at all; some of my other USB 3.0 cameras will work on USB 2.0, just downloading frames more slowly, but I couldn’t get the QHY to work reliably on USB 2.0. It just downloaded blank frames and didn’t report the temperature or cooler power correctly. Even on my USB 3.0 computer, I had some additional problems while running other cameras at the same time, although some adjustments to the USB traffic settings alleviated those issues.
Because of its small field of view, I paired it with a 400mm focal length camera lens and a 530mm focal length refractor for testing.
The QHY533M is a 9 MP, 3008×3028 sensor with a 14-bit ADC boasting 58k electron well depth with 0.0005 electrons/pixel dark current at -20C. The peak quantum efficiency of 90% blows away my four-year old ZWO ASI1600MM Pro, which only came out in 2018.
Full well capacity, dynamic range, and read noise plots can be found at https://www.qhyccd.com/astronomical-camera-qhy533/. The website also contains a lot of other important information such as system charts for adapters for different telescopes, mechanical drawings, and more specifications.
The increase in sensitivity and the low read and dark noise were obvious while I was processing images. I imaged the Helix Nebula at the Okie-Tex Star Party under very dark skies using a Nikon AF-S NIKKOR 400mm f/2.8E FL ED VR camera lens and, much to my amazement, it picked up the outer halo using LRGB filters instead of the hydrogen-alpha filter that is typically necessary to capture this detail. The default gain in the driver is 76 but I wanted to use it closer to unity gain, which from the graphs looked like 60 (I later learned that it is 68).
The noise was so low in the images I took at the star party that I barely needed to apply denoising, if at all, with a sufficient number of subframes. They were a joy to process.
The QHY533M performs equally well under heavy light pollution. I had to apply a little more denoising but images were still very easy to process. I used my own filter wheel for these images instead of QHY’s because my narrowband filters are 2” rather than 1.25”.
After ironing out a few connection issues, QHY533M monochrome camera performed reliably and solidly, and I am very pleased with the images I created with it. The 1” sensor seems small but it has the advantage of smaller file sizes, which is particularly helpful when imaging under light pollution and need many more subframes to get a nice result. The small sensor and file size would make this camera an ideal candidate for doing lucky-image deep sky astrophotography but I haven’t tried that with it yet. The QHY533M is an impressively sensitive and low-noise camera for its price point. I enjoyed using it and would consider buying one for myself!