ZWO ASI1600MC-Cool colour camera
$ FDSDEOH FDPHUD ZLWK GXDO UROHV DV D ZLGH HOG DQG 6RODU 6\VWHP LPDJHU
SKY SAYS… Is this the ultimate astro camera? Well, it does tick a lot of boxes and can be used across the board...
We have reviewed a number of cameras recently that have pushed at the boundary between Solar System and deep-sky astrophotography. ZWO’s cooled, one-shot-colour (OSC) ASI1600MC-Cool is another. However, unlike its predecessors, which have nipped at the heels of mid-resolution cooled astronomical CCD cameras, this CMOSbased device has a 4656x3520 pixel (16 megapixel) sensor that takes a serious swipe at cooled largeformat OSC CCD devices and DSLRs.
Its full resolution is best suited for deep-sky imaging and its large format sensor certainly gives a DSLR-like experience. Shooting the Orion Nebula through a 130mm f/3.3 astrograph, we had no difficulty in fitting the entire sword region on chip in one go. Despite the camera’s relatively small 3.8µm pixels, we found its sensitivity to be excellent, as was its colour rendition. It was as capable of capturing the hydrogen-alpha reds in the Orion Nebula as it was the lovely blues of the reflection nebula that permeates the Pleiades open cluster.
Using the whole sensor area restricts the camera’s peak frames per second (fps) value to 23fps in 10-bit mode, or 14fps if using the increased tonal range of its 12-bit mode, which is fine for large deep-sky objects. Exposures can range from 32 microseconds up to 2,000 seconds, and typically we found ourselves working in the 10- to 60-second range while imaging deep-sky targets. With the low noise characteristics of a camera such as this, short exposures will deliver a good signal to noise ratio, which is ideal. Noise is further kept at bay via active cooling, enabled by connecting an optional external power supply. This is very efficient and can drop the temperature of the sensor to between 40 and 45 degrees below the ambient temperature. In our tests, we timed a drop from 15°C to –20°C as taking five minutes.
The clear benefit of cooling
The difference between having the cooling on and off was dramatic when we compared a –20°C cooled 900-second dark frame against a non-cooled one. It was only after a severe stretch that we could see any background noise in the cooled version, including a couple of regions of amp glow. Stretching the much noisier, non-cooled image by the same amount made it appear pure white.
For the planets, the full 4656x3520-pixel array is overkill; instead you would typically define a region of interest (ROI) to reduce the number of active pixels. With reduced data overhead, the peak frame rate limit increases. Imaging Jupiter at f/28 through a 14-inch Schmidt-Cassegrain with a ROI of 344x300 pixels