GCN Circular 9239

Arto Oksanen (Hankasalmi Obs., Hankasalmi, Finland) reports via the AAVSO 
International High Energy Network the following optical observations of 
GRB 090424 (Cannizzo et al., GCN #9223):

A. Oksanen reports the detection of the optical counterpart of GRB 090424 
approximately 6.5 hours post-burst.  Unfiltered observations were made 
using a 0.4-meter RC telescope with an SBIG STL-1001E CCD.  A total of 
sixty, 60-second observations were made having a mid-point time of 
20:45:00 UT on 2009 April 24.  The afterglow was detected with a magnitude 
of 19.1 +/- 0.1 measured relative to the R band magnitude of USNO-A2.0 
1050-06753889 (R=16.3).  Astrometry of the afterglow position yields a 
position of RA: 12h 38m 05.1s, Dec: +16d 50m 15.3s, in agreement with the 
UVOT coordinates given by Cannizzo et al. (GCN #9223).

A jpeg preview of the observation showing the position of the afterglow is 
available at this URL:

http://murtoinen.dyndns.org:8888/ccd/grb/GRB090424/GRB090424-S001-R0XX-Clear.jpg

A detailed report of the observation is available at the following URL:
ftp://ftp.aavso.org/grb/ArtoOksanen_GRB090424_2454946.42162_.txt

A FITS image of this observation is available at the following URL:
ftp://ftp.aavso.org/grb/ArtoOksanen_GRB090424_2454946.42162_.fits

The AAVSO thanks the Curry Foundation for their continued support of the 
AAVSO International High Energy Network.