So the central black circle in the CT should not exceed 30 pixels in diameter, but what would be the minimum diameter in pixels? If you can see the attachment I included in this post, the central black circle in this case (12 bit CT #3) is 5 pixels in diameter, but was not detected (and neither were two other CTs we deployed in this UAV test) in any of the dozens of images where it was visible. Alex, is it too small, are there other problems, or what is your recommendation?