Dennis Gorelik

https://youtu.be/UGL_OL3OrCE?t=1173
"So we do calibration at the same time as imaging"

~~~~~~~~~~~~
https://en.wikipedia.org/wiki/Calibration
Calibration in measurement technology and metrology is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy.
~~~~~~~~~~~~

The only image of "known accuracy" that these scientists had during black hole imaging -- was a theoretical image of how that black hole should look like.
But it is invalid to use that theoretical image as a self-proof that this theoretical image is correct.

So this team of "black hole photographers":
1) Took an extremely sparse signals from their several telescopes.
2) "Calibrated" their "signal interpretation" algorithm based on the theoretical black hole image (that they wanted to see).
3) Made "calibrated" "signal interpretation" algorithm to interpret sparse signals.
4) Not surprisingly, their "signal interpretation" algorithm produced theoretical black hole image that these "photographers" wanted to see.

What these "black hole photographers" did is NOT science, but scientific scam.

That explains why these "photographers" instead of photographing Sagittarius A (that is 26 thousand light years away) chose to photograph Messier 87 (that is 53 million light years away -- 2000 times further!)

At shorter distances there is not enough room for creative "calibration" of sparse signals.

See also:
Extracting a black hole image from "sparse telescope matrix"