Discovery Astrophotography with ZWO ASTRO



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By popular demand, we now introduce the ASI294MM, the monochrome version of the ASI294MC. Some of the highlights include:

  • Back-illuminated sensor – improving sensitivity and reducing noise.
  • 4/3” format with 4.64 um pixel size – ideal for many types of telescopes.
  • 14-bit ADC – giving high dynamic range.
  • An impressive 66ke- full well capacity.
  • 4144*2822 high resolution – with the Bin1 mode the camera can operate at a resolution of 8288*5644 and pixel size of 2.3 um.

On top of this, not only does it have a very high QE value with a peak at about 90%, but also feature an ultra-low readout noise of 1.2e. If you are looking for a small-format monochrome camera for planetary imaging, you can’t go wrong with the ASI294MM.

Sensor length*width: 19.1*13.0mm. Diagonal: 23mm.


ASI294 is the first camera in the world that equiped with SONY latest sensor IMX294CJK.


Diagonal 21.63 mm (Type 4/3) Approx. 10.71M-Effective Pixel Color CMOS Image Sensor, This is the official description on Sony website. In our effort, we remolded it to make it Diagonal 23.2 mm (Type 4/3) Approx. 11.71M-Effective Pixel.

▶High-Sensitivity Type 4/3 CMOS Image Sensor that Supports 4K for Astronomic Cameras and Industrial Applications

The “IMX294CJK” is the first in-house image sensor for astronomic cameras to adopt the Type 4/3 format, and realizes output of the number of pixels needed for 4K at 120 frame/s (in ADC 10-bit output mode, ASI294MC can run up to 25fps at 4k format base on USB3.0 bandwidth). In addition, use of a large-size pixel achieves SNR1s of 0.14 lx* which is very close to the value of ASI224(0.13 lx*).

▶Exceptional low-illumination performance

Exceptional low-illumination performance of SNR1s: 0.14 lx is realized by use of a large-size optical system and by expanding the area per pixel to 4.63 µm. This makes the IMX294CJK ideal sensor for astronomic camera market applications which requires low-illumination performance.

14bit ADC & 13 stops DR

ASI294 have 14bit ADC and it can achieve 13 stops dynamic range which is even better than ASI1600.

HCG Mode


The full well capacity of 66387e of ASI294MM is near the top of all ASI planetary cameras. It ensures a very high dynamic range of up to 13 stops that will greatly reduce the issue of overexposed images and also help to collect richer color information.

When the gain value is set to 120, the HCG high gain mode is turned on. We’re not saying it’s magic…but we’d like to think it is pretty close. With the HCG-mode turned on, the readout noise is greatly reduced, and the dynamic range is basically unchanged.


HCG mode will be on when gain is higher than 120(12db), read noise will drop below 2e but same dynamic range(13 stops).

ASI294MM Unlocked Bin1 Mode

Yet another perk of the ASI294MM is that the pixel size is switchable – you can switch between unlocked Bin1 mode and Bin2 mode anytime in your astrophotography software. The unlocked Bin1 mode changes the pixel size into 2.3um and increases resolution to 8288×5644. The ability to unlock bin1-mode was a popular request from our customers. Of course we listened to you and worked quickly to make it possible.

Remember that using Bin1 mode will decrease the full well capacity compared to the standard bin2-mode.

Unlocked Bin1: 12bit ADC, 2.3um pixel size, 47 megapixels, 8288*5644 resolution, 14k full well capacity.

Bin2: 14bit ADC, 4.6um pixel size, 11.7 megapixels, 4144*2822 resolution, 66k full well capacity.

You can learn more differences between unlocked Bin1 and Bin2 modes by comparing the performance charts.

If the sampling accuracy you get with the 2.3um pixel size falls within a reasonable range, then the unlocked Bin1 mode will help you get more object details. However, you will lose dynamic range and ADC bit depth. Also the image files you get at Bin1 will probably be around 4 times bigger than Bin2.

So in the end the unlocked Bin1 mode is double-edged, you may choose to use it or not depending on the specific circumstances during your imaging sessions.

ASI294MC Full well Capacity

63700e full well, which is 3 times than ASI1600’s capacity. Even bright stars won’t saturate under long exposure.

This camera can achieve higher SNR(signal to noise ratio) with just one single exposure.

QE Value


As ZWO’s latest BSI (backside illuminated type) mono camera, ASI294MM has very high QE performance, not only higher than its color version, but even ASI1600MM. It is estimated that the QE peak value is about 90%.

ASI294MM vs ASI1600MM


IMX294 sensor is a BSI(back-illuminated type) sensor and has very high QE(we suppose the QE peak is more than 75%).

USB 3.0 Port & ST4 Port


USB 3.0 Port: Providing 5Gb bandwidth to let ASI294MM run at 19fps (12bit, high-speed mode) or 16.3fps (14bit, normal mode) at full resolution (11.7Mega, Bin2).

ST4 Port: This can be used to connect with auto guide port of mount for guiding.


USB 3.0 Port: Provide 5Gb bandwidth to make it possible for  ASI294MC to run at 16 fps (14bit, normal mode) or 19 fps (12bit, high-speed mode)  at full resolution(11.7Mega).

ST4 Port: Can be used to connect with auto guide port of mount, for guiding.

Mechanical Diagram

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