https://phys.org/news/2018-05-anu-stargazing-world.html

The effort was so great that Guinness World Records officials were unable to confirm the final numbers on the ABC's final Stargazing Live episode.

ANU held the previous Guinness World Records title for the Most people stargazing multiple venues – just shy of 8,000 participants across 37 locations in Australia looked up to the night-sky at the same time on 21 August 2015.