TITLE: GCN CIRCULAR NUMBER: 30305 SUBJECT: GRB 210619B: Abbey Ridge Observatory optical afterglow observation DATE: 21/06/22 17:00:39 GMT FROM: Filipp Dmitrievich Romanov at Amateur astronomer Filipp D. Romanov (Russia) and David J. Lane (Saint Mary's University, Canada) report: Filipp Romanov observed optical afterglow of GRB 210619B (D'Avanzo et al., GCN Circ. 30261) remotely using 0.355-m f/6.2 Schmidt-Cassegrain telescope of Abbey Ridge Observatory (it is owned by Dave Lane) in Canada, on 2021-06-21. Eight images (with exposures: 660, 840, 720, 840, 720, 720, 780 and 720 seconds) were obtained with Cousins R filter from 02:29:26 to 04:56:00 UTC. The optical afterglow (with UVOT position) is clearly (SNR = 11) visible in the stacked image (mid time = 03:42:42 UTC, that is 1.155 days after the trigger). Romanov measured its magnitude comparing to transformed (using formula Rc=r’-0.22 from Dymock & Miles, 2009) r' magnitudes of nearby stars from Pan-STARRS DR1 catalogue (Chambers et al., 2016). The measured magnitude = 20.0 +/- 0.2. Magnitude was not corrected for Galactic extinction. Stacked image available here: http://www.abbeyridgeobservatory.ca/images/GRB210619B.jpg