TITLE:   GCN CIRCULAR
NUMBER:  33635
SUBJECT: GRB 230307A: iTelescope optical upper limit (likely)
DATE:    23/04/16 15:31:19 GMT
FROM:    Filipp Dmitrievich Romanov at Amateur astronomer  <filipp.romanov.27.04.1997@gmail.com>

On 2023-03-09 I observed the field of GRB 230307A (Fermi GBM team, GCN
Circ. 33405) remotely using the telescope T17 (0.43-m f/6.8 reflector
+ CCD) of iTelescope.Net in Siding Spring Observatory (Australia). Ten
images with exposures of 300 seconds and Ic filter (Astrodon
Johnson-Cousins Ic) were obtained, the midtime of the stacked image is
10:52:40.7 UT (1.8 d. after the trigger). I did not detect a clear
optical afterglow near the Swift-XRT position (Burrows et al., GCN
Circ. 33465), but in this area in the stacked image there is what I
can consider a noise (SNR <2), but I do not exclude that it may be
faint afterglow near the upper limit of about 20 magnitudes in this
band.