ESO study quantifies impact of proposed satellite constellations on astronomy (eso.org)

• Over 1.7 million satellites proposed, including bright mirror satellites.
• Study: no more than 100,000 faint satellites (mag > 7) acceptable.
• Reflect Orbital satellites would be 4x brighter than full Moon if directly illuminated.

"A new ESO study by Olivier Hainaut, accepted for publication in Astronomy & Astrophysics, calculates that planned satellite constellations—including SpaceX's one million satellites and Reflect Orbital's 50,000 mirror satellites—would severely impair ground-based astronomy. The study recommends limiting total satellites to 100,000, all fainter than visual magnitude 7, to avoid compromising observations. The full Reflect Orbital constellation would increase sky brightness three to four times, and even without direct beam, each satellite would appear as bright as Venus. The findings have been submitted to the US FCC as part of regulatory proceedings."