ZWO ASI294MC Pro Review
The ZWO ASI294 MC Pro is a remarkably capable one-shot-color CMOS camera for deep sky astrophotography. Whether you use it for broadband true-color images on a moonless night or ultra-long-exposure images using your favorite narrowband filter – this camera can produce insanely beautiful images.
This is easily one of the best color cameras I have ever used for astrophotography, and my go-to choice for a night of deep sky imaging. Over the past year, I have used this camera extensively through a number of telescopes in the backyard and beyond.
Here is a taste of what the ASI294MC Pro can do:
The Trifid Nebula using a Luminance Filter with the ASI294 MC Pro
This photo of the Trifid Nebula was captured using the ZWO ASI294MC Pro with an Astromania Luminance filter (IR Cut) in front of the sensor. The photo was captured under the dark skies of the Cherry Springs Star Party in 2018.
The ASI294MC Pro has proven to be an incredible 4/3 sensor CMOS astronomy camera in the astrophotography community. This camera is responsible for my best deep sky images to date, including the photos shown below.
It is the best camera I have ever personally used for astrophotography, and I continue to use it to this day. At under $1K (US), you’ll be hard pressed to find a more versatile, reliable, and easy-to-use color astronomy camera.
This camera works exceptionally well with broadband light pollution filters, and narrowband filters. Many people will advise you not to use a color camera with narrow bandpass filters such as H-alpha or OIII, but I have found the 294MC Pro to perform extremely when used with a duo-narrowband filter.
If you want to see what others are doing with the ASI294MC Pro, have a look at the #ASI294MCPro hashtag on Instagram, and you’ll see that it’s not just me. You can also see exquisite example images with this camera on Astrobin.
ASI294MC Pro Astrophotography Camera Review
I can safely say that I now know exactly what the ASI294MC Pro is capable of, and some recommended settings that you can use for a successful image. I’ve used this camera for both full-color images with light pollution filters, an IR cut filter and narrowband filters that separate certain wavelengths of light such as Ha and OIII.
This OSC (One-shot-color) camera performs exceptionally well in both situations. The idea of capturing narrowband images with a color camera is something that is generally advised against in the astrophotography community. This is because a color sensor will essentially record about one-quarter of the detail a mono camera would.
The cheat code, however, is to use a color camera like the ASI294 MC Pro with a duo-narrowband filter like the STC Astro Duo-Narrowband filter. This has the power to build gorgeous deep sky images like the Eagle Nebula example below in a single shot.
The Eagle Nebula in Ha + OIII (STC Astro Duo-Narrowband Filter)
The photo above was captured in a Bortle Scale Class 8 light polluted area (my backyard) using the ASI294 MC Pro. It showcases both Ha and OIII gases of this Emission Nebula (Messier 16) for some astonishingly detailed results from the city.
This dedicated astronomy camera houses a high-sensitivity type 4/3 CMOS image sensor that supports 4K output at 120 frames per second. It’s a SONY 10.7 MP sensor that produces high-resolution 4144 x 2822 pixel images at its native resolution.
I generally bin my images 2×2, so that just means that my photos are half of that size, in greater resolution. (smaller pixel size). The Bayer pattern of this color sensor is RGGB, which you’ll need to remember when selecting the camera in your image control software, and before stacking.
This camera is well suited for color EAA astronomy (Electronically-Assisted Astronomy), as the ASI294MC Pro includes a 256MB DDR3 memory buffer to help improve data transfer reliability. This is a great feature to consider if you plan on diving into this type of visual astronomy.
You can benefit from the high sensitivity sensor to view more detail in a deep sky object in a “live” looping video feed. Because I am obsessed with collecting images, the only time I experience a glimpse of this feature is when I am framing my target!
Comparing Specs Between ASI Color Cameras:
|ASI183MC Pro||SONY IMX183||1"||20 MP||Check Current Price|
|ASI294MC Pro||SONY IMX294||4/3"||10.7 MP||Check Current Price|
|ASI071MC Pro||SONY IMX071||APS-C (1.8")||16 MP||Check Current Price|
|ASI128MC Pro||SONY IMX128||Full Frame (35mm)||24 MP||Check Current Price|
All of the Pro model ASI color cameras include the DDR3 Buffer technology which results in faster data transfer speeds and reduces amp glow. Each one of these cameras requires 55mm of back focus between the image sensor and your flattener/reducer.
In the case of the Celestron 8″ RASA F/2, no field flattener is needed as this optical system is very flat to begin with. However, a new backfocus distance is needed between the camera sensor and the top surface of the lens group cell. To achieve the required spacing of 29mm for the RASA, I used a Starizona filter slider drawer to give me some added backfocus.
Making the Upgrade from a DSLR to a CCD-style camera
When I began using color CMOS cameras like the ASI294 MC Pro, I could no longer use the camera control software I did with my DSLR’s (Backyard EOS). Instead, I use an application called APT (Astro Photography Tool), which allows me to control every aspect of the camera from the cooling temperature to gain.
Upgrading from a DSLR to a CCD type astronomy camera like this is a big transition. For me, the hardest part was getting used to controlling the camera entirely with external software.
The change in image file formats (from .RAW to .FIT was also a bit of a hurdle early on. Luckily, DeepSkyStacker is well suited to stack and de-Bayer this image format into a high resolution .TIF file that you can process in Photoshop.
The two-stage TEC (Thermo-electric cooling) is perhaps the biggest difference and advantage a dedicated astronomy camera has over a DSLR. As you may know, noise is a big issue to deal with when taking long exposures at a high ISO. I’ve battled with noise for many years (and continue to do so) when processing my astrophotography images taken with my Canon T3i and 5D Mk II DSLR’s.
A cooled CMOS camera like the ASI294 MC Pro can cool its sensor down to 35 degrees below ambient. This results in images that are virtually free of thermal noise. I should mention that it’s important to understand that this means 35 degrees below the current temperature, so if it’s a hot 30-degree night, the camera will max out at -5 degrees.
The ASI294MC Pro Camera attached to my Explore Scientific ED102 Refractor Telescope
The pixel size of the ZWO ASI294MC Pro is a great match for many of my astrophotography telescopes. The pixel size of the ASI294 is 4.63µm, which is in the middle of the road for the ASI camera lineup. For comparison, the ASI183MC Pro has a sensor with a 2.4µm pixel size.
So what does this mean for your astrophotography images?
In the amateur astrophotography community, a general rule of thumb is to use a pixel scale that is between 1.0 to 2.0 to be “well sampled”. This is simply a rough guideline and should not be taken too literally. The math for calculating the pixel scale of a particular camera and telescope combination is:
pixel size (4.63) / focal length (550) x 206 = 1.73
When using the ZWO ASI294MC Pro with the Celestron 8″ RASA F/2, I have a pixel scale of 2.38 which some consider to be “under-sampled”. Theoretically, under sampling can lead to blocky or pixelated stars in your image, although in reality I have never known this to be a noticeable problem (in any of my telescopes).
Compare this to the Sky-Watcher Esprit 100, which provides me with a pixel scale of 1.73. The bottom line is, it’s worth calculating the pixel scale of your camera and telescope combo before making any big decisions. In my experience, the ZWO ASI294 is an extremely versatile choice for many telescope focal lengths.
The Cocoon Nebula in Broadband RGB. Sky-Watcher Esprit 100 and IDAS NGS1 Filter.
Connections and Software
The camera is connected to my computer via a USB 3.0 cable. For the cooling feature, it also requires an external 12V power supply that does not come included with the camera. If you’re anything like me, you have accumulated a number of 12V adapter cables over the years.
To keep things organized and convenient, I now connect the power port on the ASI294MC Pro to the outlets on my Pegasus Astro Pocket Power Box. This means that the camera and telescope don’t have another power cable running to an outlet. It all rides atop the iOptron CEM60 equatorial mount.
The camera is controlled using APT, which required the appropriate drivers from the ZWO ASI website. Installing the driver is painless, and then the “ASI camera” selection will appear from the drop-down menu the next time you connect the camera to APT.
The cooling function is set using the “Cooling Aid” within Astro Photography Tool. It can take a few minutes to get the camera sensor to the temperature you want it. It’s best to get a head start on this process so you’re not waiting around when it’s time to shoot.
A One-Shot-Color Camera – Impressive Specs
I love how sensitive the SONY IMX294CJK sensor is on this camera. The dynamic range of this camera sensor is listed at 13 stops. This is even more than the legendary AS1600 camera from ZWO. This characteristic is thanks to the built-in 14bit ADC (analog-to-digital converter) unit on the 294MC Pro.
ZWO ASI294MC Pro Camera Specs:
- Sensor: 4/3″ SONY IMX294 CMOS
- Diagonal: 23.2mm
- Resolution: 10.7 Mega Pixels (4144 X 2822)
- Pixel Size: 4.63µm
- Bayer Pattern: RGGB
- DDRIII Buffer: 256MB
- Back Focus Distance: 6.5mm
- Cooling: Regulated Two Stage TEC
If you’re wondering what the difference is between the MC-Cool and MC-Pro cameras from ASI are, it’s the DDR3 memory buffer. For non-tech-heads (like myself) this basically means that the camera can transfer data faster and more efficiently. It also reduces amp glow because this artifact is primarily caused by slow transfer speeds.
Here is what the amp glow looks like on a single image captured with the ASI294MC Pro. The amp glow is completely removed after stacking the images with dark frames in DeepSkyStacker.
Recommended settings for the ASI294 MC Pro
I find that the best camera settings to use with this camera are to set the gain at “unity gain” and an exposure length of 3 to 5 minutes. This, of course, depends on the deep sky target you are shooting, and the filters being used with the camera.
For example, using a narrowband filter such as a 12nm Ha, I would choose an exposure length of at least 5 minutes. I even shot some images that were as long as 10 minutes with this camera. The photo below shows the Rosette Nebula using a stack of 20 x 10 minutes exposures using the ASI294MC Pro and an Astronomik 12nm Ha filter.
Because the sensor is so sensitive, I can often find my deep sky target in a 2-3 second exposure in live loop mode. This is usually with a strong narrowband filter in front, which is quite impressive. This makes framing the target much easier because you’re able to see the shape and orientation of the DSO (almost) in real time as you adjust the telescope.
Taking flat frames with the ASI294MC Pro
I use 3 layers of white t-shirts when capturing flat frames with the ASI29MC Pro. I point the telescope towards the morning dawn sky with the t-shirts covering the telescope objective.
When the white t-shirt method isn;t cutting it, a flat field panel like the Artesky Flat Field Generator works exceptionally well.
Taking flat frames with the ASI294MC Pro using a flat field panel (Artesky Flat Field Generator).
I use the CCD Flats Aid tool in Astro Photography Tool to find the correct exposure to hit my target ADU (25,000). In my experience the images are usually around an exposure of 0.03381 when using a gain setting of 120 (unity gain). This creates a flat field image with an ADU of approximately 25000.
I have heard that others have found success by using longer flat frame exposures, which can be accomplished by adding more layers of white t-shirts or with an adjustable flat panel.
If you compare the ASI294MC Pro vs. the ASI071MC Pro, you’ll find that the price is significantly more affordable for the 294. I’ve used both of these cameras (The ASI071 camera was the older non-pro “Cool” version), and the image results are remarkably comparable.
The biggest difference between the two cameras is, of course, the sensor itself. The sensor in the AS071 is a 16MP APS-C sized chip, while the ASI294 is a four-thirds 10.7 MP sensor. This changes the pixel scale of your images and thus the apparent size of the objects you’ll capture through your telescope.
For APO refractors in the 700-1000mm range, the pixel scale of the ASI294 MC Pro was the absolute perfect size for some of my favorite deep sky targets like the Eagle Nebula and Pelican Nebula. I used a Starfield 0.8X reducer/flattener with this camera and the various refractor telescopes I used when imaging deep sky objects.
If you’re looking to upgrade your DSLR or current color astronomy camera to the realm of “cooled” CMOS sensors – my results with the ASI294 MC Pro should help you make a more informed decision. I highly recommend the ASI294 MC Pro camera if you are in the market for a color astrophotography camera with some serious power and versatility.
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