At ~200 m2, these things are going to be very bright. The prototype BlueWalker 3 (64 m2) reached an apparent magnitude of +0.4.
"The #FM1 marks AST’s first attempt at sending up a second-generation BlueBird #satellite, which spans around 200 square meters — or about three times the size of the company’s first-generation BlueBirds. The FM1 weighs in at nearly 13,000 pounds and features a "phased array antenna" at about 199 square meters, letting it operate as a cell tower in space." (via @PCMag)
https://www.pcmag.com/news/despite-spacex-protests-fcc-clears-ast-spacemobiles-massive-satellite
