TITLE: GCN CIRCULAR NUMBER: 29165 SUBJECT: GRB 201223A: iTelescope optical afterglow observations DATE: 20/12/24 02:49:44 GMT FROM: Filipp Dmitrievich Romanov at Amateur astronomer I observed the field of GRB 201223A (Gropp et al., GCN Circ. 29158) with remote telescope T18 (0.32-m f/8.0 reflector + CCD) of iTelescope.Net in observatory AstroCamp at Nerpio (Spain) on 2020-12-23 since 19:49:22 UT (1 hour 50 minutes 56 seconds after the trigger). 5 images (with exposures 300, 120 and 180 seconds) were obtained with Astrodon luminance filter and 4 images (exposures: 300 and 60 seconds) with photometric Johnson V filter. I detected the optical afterglow in images with position: RA 08:51:09.46 Dec +71:10:47.00. It is not present in the Pan-STARRS images. The following magnitudes were measured from comparison to r magnitudes of nearby stars from Pan-STARRS DR1 catalogue (Chambers et al., 2016): Time of start (UT) Exp.time (s.) Bin. Mag. r Mag. error Filter --------------------------------------------------------------------------- 19:49:22 300 1 19.2 0.2 Luminance 19:56:25 300 1 19.3 0.4 V 20:26:25 300 2 19.9 0.4 V 20:33:07 300 2 20.1 0.3 Luminance --------------------------------------------------------------------------- Magnitudes were not corrected for Galactic extinction. Stacked image (4x300 + 2x120 + 180 sec.) available here: https://www.flickr.com/photos/filipp-romanov/50753199496