TITLE: GCN CIRCULAR NUMBER: 22988 SUBJECT: GRB 180720B: LCO optical afterglow observations DATE: 18/07/21 04:59:42 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst Nicolas Crouzet (IAC) and Daniele B. Malesani (DAWN/NBI and DARK/NBI) report: We observed the optical afterglow of GRB 180720B (Siegel et al., GCN 22973; Martone et al., GCN 22976) using the 0.4-m telescope located at the Teide Observatory, part of the Las Cumbres Observatory (LCO) telescope network. A single 600-s exposure in the SDSS r band was obtained with mean time July 21.094 UT (0.495 days after the GRB). The PSF of the image is not optimal, being double-peaked. Aperture photometry, compared to nearby stars from the Pan-STARRS catalog, provides for the afterglow a preliminary magnitude r = 17.85 +- 0.10 AB.