Ever since SBIG ST-4000XM camera was introduced, I wanted a camera with a square sensor to play with. Such CCD based cameras are quite expensive, so I really couldn't justify buying another one just because of an interesting sensor format. But now there are several affordable options based on Sony IMX533 CMOS sensor available. I could finally get one without going broke. Such cameras are available from QHY, ZWO, and then there is a bunch of cameras made by ToupTek Photonics and branded as Omegon, Altair, TS-Optics, RisingCam, ... For no particular reason I decided to get an Altair branded one (OK, that camera has the most interesting color, I admit).

The full name of the camera is Altair Hypercam 533C. It is a bit larger than ZWO or QHY models, but it is rather light for its size. Usually when something is lighter than expected that makes me a bit suspicious, but build quality of the camera is decent, nothing to complain about there. Camera is delivered in a serviceable hard case, with all the necessary cables and power supply included. It is single-shot color camera, with Bayer matrix on the sensor. Regulated dual stage thermoelectric cooling can cool the sensor more than 40 °C below the ambient temperature. At the back of the camera there is one USB 3.0 port for connection to the PC, USB 2.0 hub for accessories and power connection. There is no ST-4 guiding port. Unlike some other cameras, this camera will not work without a power supply.

The camera is equipped with a heated optical window, which is also an UV/IR filter. My only real complaint about the camera is that the heater is not strong enough to prevent dew forming on the window in some circumstances. The ugly contraption on the camera is an external heater that solves that problem.

Sony IMX533 CMOS sensor has 3.76 × 3.76 µm pixels and resolution of 3008 × 3008 pixels. Image area is 11.31 × 11.28 mm. It is a back illuminated sensor with 14 bit A/D converter. Thanks to back illumination the sensor has high sensitivity and dynamic range. Dark frame produced by the sensor is very clean with no amplifier glow visible, even at longer exposures. Its square shape makes framing of objects very easy and enables optimal use of best corrected central area of an image. Moderate sensor size, together with square shape, is rather forgiving on optics, so good results can be had without expensive setups (unlike larger sensors where the area of well corrected image must be much larger). The sensor Bayer matrix type is RGGB, which is good to know for debayering process.

For DSO imaging I get the best results with camera gain set at 250 (0.8e/ADU) , taking sub-frames up to 3 minutes long. With this camera there is really no practical limit to the length of a sub-frame, but the longer the sub-frame is the more likely is that you will get a satellite or plane trail in the image, or encounter guiding issues. Since read noise of the camera is low, hundred or more of sub-frames can be stacked to get images with good signal to noise ratio.

Here you can see the external dew heater from the front. The heater is also produced by Altair. It is an accessory that I strongly recommend, otherwise dew forming on the outside of the optical window might ruin your imaging session.

This camera being rebranded ToupTek one, it doesn't have as many dedicated accessories as some other ones do. But, if you take care of backfocus requirements, there is no problem in using generic accessories or even accesories for other cameras. The camera has T-thread for connection to the telescope, and its back-focus is a very common 17.5 mm.

Here you can see the camera connected to a medium format Pentax camera lens, using couple of adaptors: from Pentax 67 to Nikon, then QSI adapter from Nikon to T thread and then finally Altair filter holder (T-thread on both sides, also used to get the proper distance from the lens to the camera).