THO reasearch team managed to observe and photograph the after glow of the GRB 130831A about 7 hours after Swift-telescope discovered it. Markku Nissinen and Harri Vilokki took photos that clearly shows the GRB. The exopsure times were 600 seconds and according the measurements the brightness of the GRB was about 18.01 magnitudes. The measurements were made by combining six individual photos. The measurement is in line with other measurements made by other observatories. At the time of discovery the GRB was about 14 magnitudes bright. THO measurement has been published in GCN 15156 circular.
In the picture below GRB130831A is marked with arrow and second arrow shows the comparison star NOMAD1 1194-0619856.