10/17/2021 Update -

I have updated the image of this post.  My original post attempted to make things easier for comparison by aligning the images to be the same size, specifically by aligning the 294 image to the 6200 image.  This was a bit unfair to the 294 image, in that the alignment caused some minor blurring of its pixels.  The new image maintains the original size of each image, resulting in a truer comparison of the results of the 2 cameras.  I have also added a binned 2x2 6200 image for completeness.

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The ZWO ASI mono cameras, ASI6200MM and ASI294MM, are both excellent cameras.  The specs are at the bottom of this description.  I wish I also had the ASI2600MM for comparison, but I sense from what I read that its performance is similar to the ASI6200MM.

I did not include a comparison of QE curves in the spec table because I am not confident in the accuracy of anything I have seen regarding QE, particularly since that data is not provided by Sony.  I sense they are fairly similar for each camera, with perhaps an edge to the 294.  The data in the table is for the binning modes that most people (including myself) will use for these cameras – binned 1x1 for the 6200 and binned 2x2 for the 294 – based on the image scale. 

The 6200 has a much larger sensor (full frame) and is much more expensive.  It has basically no amp glow.  The resulting background for the 6200 is very smooth compared to the relatively blotchy background for the 294.

I like both of these cameras.  For larger DSOs, there is no question but to use the 6200 and its lovely large sensor.  But what about for small objects, where the 294 sensor size is adequate?

For the past year, I have used my 294 for small objects.  Why?  Each week I get that question.  One reason is that I don’t need the extra sensor space of the 6200, so the downloading, processing and archiving of images is much faster using the 5x smaller 294 subs.  But the more important reason for me to use the 294 is that I believe that it gives better slightly results than the 6200 for small objects.  I have done many comparisons and, in my view, the 294 results are consistently better.  I am not sure why, based on the camera spec data.  

I have attached an image which shows a sub comparison, using both cameras and my C11 setup.  The galaxy is about 2 arc-minutes wide. The comparison is using a typical raw uncalibrated lum sub with a standard stretch.  The seeing was good for each of these images, taken on subsequent nights.  I used the same exposure length of 120 seconds for each sub and each camera's unity gain settings (0 for 6200, 120 for 294).

From my perspective, both the bright stars and the dim background of the 6200 image appear to be better.  But for the mid-range brightness of the galaxy disk, I see more detail in the 294 image.  Once a lot of subs are stacked, I feel that the 294 has even more advantage - the details in the mid-range pop out even more, and the blotchy background becomes smoother.  This is just one object, but I have seen similar results whenever I do these comparisons. 

Please let me know if you have any comments or questions.  I am documenting this comparison mainly for my own use, but I thought I would share it since others have asked me about it.

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Camera Specs

Camera                          ASI6200MM               ASI294MM
Sensor                           Sony IMX455            Sony IMX492
Sensor Size (mm)               36x24                       19x13
Resolution                       9576x6388                4144x2822
Pixel Size (um)               3.76 (1x1 bin)         4.63 (2x2 bin)
ADC                                        16 bit                        14 bit
QE                                            N/A                          N/A
Full Well                                51400                       66000
Price                                      $4000                      $1480