https://www.cnet.com/news/first-ever-image-of-a-black-hole-is-basically-the-eye-of-sauron/

"The observations were a coordinated dance in which we simultaneously pointed our telescopes in a carefully planned sequence," says Marrone, who traveled to Antarctica several times to integrate the South Pole Telescope into the EHT array. 

Rather than a single observatory, the EHT image is the product of eight radio telescopes in Hawaii, Arizona, Chile, Mexico, Spain and the South Pole synchronized to form an array called a Very Large Baseline Interferometer (VLBI). The basic concept is to combine the signal strength of the observatories on different corners of the globe to form an array as wide as Earth itself.