TITLE: GCN CIRCULAR NUMBER: 30204 SUBJECT: GRB 210610B: KAIT Optical Detection DATE: 21/06/11 17:06:02 GMT FROM: Weikang Zheng at UC Berkeley WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to the Swift GRB 210610B (Page et al., GCN 30170) starting at ~10.46 hours after the Swift trigger (Page et al. GCN 30170). A total of 60x60s images were obtained in the clear (roughly R) filter. The optical afterglow (e.g. Page et al., GCN 30170) was clearly detected in each single image. We measured its brightness of 18.07 +/- 0.05 mag at 10.46 hours after burst, and decayed to be 18.27 +/- 0.06 mag at 12.20 hours after burst, calibrated to the Pan-STARRS1 catalog.