Swift detected the GRB060418 at 03:06:08.20 UT; the location information was made available at 03:06:33 UT (25s later).
FRAM observed this burst in completely automatic mode, driven by RTS2. It is it's 105th GRB received and processed (not all were observed). The slew took 28s, making the final observational delay 53s.
We obtained first 6 20s, then 5 40s and futher many 60s exposures. The object is not detected on single image observations. We therefore combined the images by 2, 3, 4 and 5 to get a better signal to noise ratio and analysed the images again. We found the OT reported by Falcone et al. (GCN 4966) on several images obtained this way.
The observing conditions were not perfect - a thin variable cirrus worsened the limiting magnitude by about 1-1.5.
The received points were fitted with a broken power law of the form t^(+1/2) before Tm and t^(-alpha) after Tm. Tm is the time of transition of the typical frequency nu_m of the forward shock emission through the observed frequency (R-band).
For the fitting, we used the decay rate reported by Nysewander et al. (GCN 4971) and Cobb (GCN 4972). The fitted curve reproduces well the points reported by Koppelman and Nicholson (GCN 4977).
The fit gives Tm=(300+-100)s and peak brightness R~=13.8mag. We reported this observation in a GCN Circular (Jelinek et al. 2006, GCNC 4976).