TITLE:   GCN CIRCULAR
NUMBER:  33705
SUBJECT: GRB 230427A: Osservatorio Astronomico Nastro verde upper limit
DATE:    23/04/28 15:20:54 GMT
FROM:    Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde@gmail.com>

Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy
in a large collaboration with:
M.G. Dainotti (National Astronomical Observatory of Japan), 
Y. Niino (Tokyo University, Institute of Astronomy), 
K. Kalinowski (Aarhus University, Department of Physics and Astronomy),
B. De Simone (Universita' degli Studi Di Salerno)
report: 

We image the field of GRB 230427A detected by SWIFT(trigger 1165948)
with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy. Member of: 
AAVSO - American Association of Variable Star Observers.
UAI/SSV - Unione Astrofili Italiani/sezione stelle variabili.
AstroCampania Associazione

The observations started at 19:04 UT of  2023/04/27, after 8,30 hours after the GRB trigger, at the end of twilight
with principal telescope  SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME
I took 32 image of 120 sec each. All images are unfiltered, calibrated with masterdark and masterflat,stacked with Tycho Tracker software
We have not detected any clearly visible sources, up to 20th magnitude with lightly hazy skies and lunar disturbance
Start T0+                End T0+       Rlim
19:04:53 UT            20:22:52 UT      20

We did not found any optical counterpart in the error box of the XRTcandidate.
Troja et al., GCN 33687



Magnitudes were estimated with the Gaia DR2 cat. and 
are not corrected for galactic dust extinction.



The message may be cited.