–part 8 of the essay An astronomer in Texas–
Our visibility was extremely poor in the following night, i.e. while we couldn’t detect a cloud with our sky surveillance camera, stars appeared to be much fainter than they should be. Since we wanted to do spectroscopy where every photon counts, this was a huge problem. I therefore went outside to take infrared images which is when we finally realized what was going on. Seen here, the pink glow in the sky is created by ash particles that were now spread evenly across almost the whole sky. The full moon provides illumination for the ground while the sky appeared utterly dark in the visible.