Radio telescopes. While I don't know the complete process of how an image is created, it's likely a composite of hundreds of thousands of points where radio wave strength was measured.

A very basic explanation is that each radio antenna likely takes a reading of some kind for each equivalent pixel in the resulting image. Over time, you can build an image.

Again, I don't know the full details of how the full image is recreated. It seems super complex reassembling millions of data points from antennas that are located on a rotating earth that is also rotating around a sun. The position of the earth probably has a huge impact on radio signal strength at any given time.

[–] JATtho@lemmy.world 4 points 2 weeks ago* (last edited 2 weeks ago)

They could be very well using the earth's orbit around the sun to get better resolution - two data points from opposite sides of the orbit. What I know is that the largest "virtual" radiotelescope is literally the size of earth. The data points are synced with atomic clocks (or better), and a container of harddrives gets shipped into a datacenter to be ingested. Thats hundreds of streams (one per antenna) of data to be just synced up, before the actual analysis even can begin. (I'm just guessing after this) At this point, you have those hundreds (basically .wav files) lined up at timepoints they were sampled (one sample, one timepoint column). So row by row, so you can begin to sort out signal phase differences between the source rows.

I.e to put it shortly: an image is not taken, it is inferred and computed. Not that you even could in the first place, it's a blackhole after all.