The ZWO ASI294 MC Pro is a color cooled sensor CMOS based camera from CMOS astronomy camera specialist, ZWO. The ASI294 is one of many CMOS cameras in ZWO’s lineup which has been of excellent quality and produces great images. The ZWO ASI294 is one of the newest cameras from ZWO, however, this model uses a color sensor instead of the more common monochrome amongst astrophotographers.
The ASI294 is a camera designed for beginning and intermediate astrophotography with its color sensor, easy to use interface and high sensitivity sensor which can let you produce great images at a relatively cheap cost, however, the camera may not appeal to more serious imagers that desire a monochrome camera, and unfortunately at the time of writing there is no monochrome model of this camera.
The ASI294 includes many of the features found in the older ASI1600 camera from ZWO, and even from the outside it may look identical, however, it houses a much different sensor which can make a huge difference in astrophotography.
The 294 is supposedly the best color deep-sky camera out there, beating the ASI1600MC but that is what I will be discussing in this review.
Technical Specs of ASI294
The ASI294 as discussed earlier uses a CMOS sensor, which is the main chip at the front of the camera that collects light. A CMOS sensor is a relatively new type of chip that has only become popular recently in cameras from ZWO and QHY, with the ZWO ASI 1600 being the first camera to bring CMOS sensors into the world of deep-sky astrophotography. CMOS cameras are most well known for their incredible sensitivity and noise levels when compared to older CCD designs.
The ASI294’s sensor has a size of micro 4/3rds, which is smaller than the sensors you would find in APS-C format cameras, like most entry-level DSLRs but much larger than say mobile phone sensors which are relatively tiny. It has a resolution of 11.3 megapixels or 4144 x 2822 pixels, meaning that you can take close to 4k resolution images with this camera which you can present on large prints or high-resolution screens without your images being blurry. It is also a color sensor, which can be a blessing or a curse but that is something I will discuss later.
This camera has a pixel size of 4.63 um, meaning every individual pixel is 4.63 micrometers across. This is around standard for astrophotography, and you will see that this is the reason that the 294 has a lower resolution sensor compared to a camera like the ASI1600 with the same size sensor.
Very importantly, you will also find a well-powered cooling system at the back of this camera. The ASI294 uses a Thermo Electric Cooler (aka TEC or Peltier chip) which takes the heat generated by the sensor over time, and moves it to the other side of the chip, leaving the sensor cool. With the ASI294, the cooling system is very powerful and the TEC can take the sensor down 35 degrees below the outside temperature.
A cooling system is important for astrophotography, as in-camera sensors a large source of image noise or grain comes from the heat either from the outside air or from the camera heating itself up after long uses, like an overnight imaging session. Cooling the camera sensor down is an essential step used to reduce levels of noise in astrophotography. This camera can cool to 35 degrees C below ambient which will greatly reduce sensor noise.
What’s different about this camera?
The ASI294 has to have features to make it worth buying over its competitor the ASI 1600, and there are some great reasons for you to want to buy this camera. Most things are the same, but the sensor is what makes or breaks a good camera. In this section, I will talk about the new sensor and some other features that may interest you.
First of all, the ASI 294 has an estimated quantum efficiency of over 75 percent by ZWO! The quantum efficiency of the camera is the percentage of incoming photons (light particles) that hit an individual pixel and are converted to electrons (electric signals in the image). Having a quantum efficiency of ~75% means that ¾ photons will be converted into electrons while imaging, which is better than even the ASI1600 camera, which only has a QE of 60%! Quantum efficiency is important especially for astro imaging because you are imaging the faintest objects even detectable with a camera, and as such gaining 10 – 15% more efficiency can make a huge difference to your exposure times and noise levels, meaning you can capture fainter objects faster.
The ASI294 has a full well depth of 67000e-, which might sound very confusing and you would be right, but that is a very important number that I will explain. First of all, a full well depth is the number of electrons the camera can take in on each pixel before completely capping out and reading out a completely white pixel. In an ideal world, you would be able to expose forever and still retain data, but the processing chip on cameras is what limits this. The number of 67000e- means that each pixel can take in 67000 electrical signals, or using the QE we discussed before 83,750 photons. The full well depth comes into effect when you have bright stars in the field, as stars will cap off much faster than nebulae or galaxies. This is an incredible improvement over the ASI1600 which has a full well depth of only around ⅓ the ASI294!
The ASI294 also includes a base noise level of 1.2e-, which is equivalent to the ASI1600 but when you consider the other improvements found with this camera it truly does beat the ASI1600.
You will also find a DDR3 buffer of 256MB, meaning that unlike older camera models, the 294 can store images if something goes wrong in between exposures so you never lose any data.
Using the ASI294
The ASI294 like other ZWO cameras comes with the features you know and love for imaging, some of them I have listed here which make astrophotography a breeze for those using this camera.
The camera has USB 3.0 which makes downloading frames on your computer super speedy, with a low risk of losing precious data. Speaking of USB ports, the camera has an onboard USB hub with two USB 2.0 ports so you can plug in two extra devices without using up more USB ports on your laptop. You might want to use these ports with devices that do not require high-speed connection such as a filter wheel or auto focuser.
The camera has full ASCOM compatibility, meaning that practically any capture software of your choice can be used with this camera. You can take videos in programs like Sharpcap and Firecap, and even polar align from Sharpcap if your telescope’s field of view is wide enough. I recommend using the camera with deep-sky capture programs that have ASCOM support, like SGP, NINA, APT and so on, powerful capture tools that you can use to set up sequences overnight to take photos without having to press a button if you are more serious about astrophotography.
The ASI294 comes with many adaptors and threads meaning that it is compatible with many standard formats. In the box you receive a USB 3.0 cable for connecting the camera to your device of choice, multiple T2 adaptors and extenders which are useful to create the ideal spacing between the camera and your coma corrector/field flattener, a 1.25” nosepiece, useful for if you do not have a T2 threaded focuser and instead a 1.25 eyepiece tube, and various other useful adaptors. You should be able to be up and running in no time as the camera comes with many useful adaptors and threads.
The ASI294 also allows you to image at 19FPS with the full sensor, which could be useful for the moon, or even faster for planetary imaging if you crop in which is a feature in Sharpcap and Firecapture used to increase your FPS. This may not be useful for many people but for applications like EAA(electronically assisted astronomy) viewing where fast images are useful so you can view the night sky with a screen, then this camera has potential.
Unfortunately, we have to address the elephant in the room: the ASI294 is only available in color variants. This as mentioned earlier in the review this is a blessing and a curse.
Color, on one hand is great, as It allows you to take color images without the hassle of using things like filters, which can become quite expensive fast when you also weigh in the filter wheel. Color also means that you need fewer files, therefore less space on your pc and by extension, less time processing all of those files is required. The camera simply spits out color images, no fuss about it.
However, on the other hand, we have the many disadvantages a color sensor causes us. The color is created by filtering the light with a Bayer matrix, which covers every pixel with a colored filter. These filters, unfortunately, block a fair chunk of the light reducing the total light intake to about 25%. Monochrome allows astrophotographers to either image the whole spectrum of light or use custom filters to image a large portion of the sensor for color or even filter out specific wavelengths emitted by nebulae.
I believe that the ASI294 is an excellent color cooled camera from ZWO, and is absolutely a great improvement over 1600 with its greatly improved quantum efficiency and sensitivity so you can pick up much fainter photon levels, amazingly high full well depth allowing you to expose much longer without clipping stars, great software compatibility, and USB 3.0 speeds.
However as this camera only comes in a color model, that is a large make or break part of this camera, which is really up to what you prefer, your imaging style and if you are more or less “serious” about astrophotography. That, however, should not detract from the fact that it is one of the best color astronomy cameras on the market.