TITLE: GCN GRB OBSERVATION REPORT NUMBER: 217 SUBJECT: GRB 990123 Optical Follow-Up DATE: 99/01/25 08:19:31 GMT FROM: Jin Zhu at Beijing Obs GRB 990123 Optical Follow-Up J. Zhu, J. S. Chen, and H. T. Zhang, on behalf of the Beijing Astronomical Observatory GRB team report: "We observed the GRB 990123 OT (GCN #202) during Jan. 24.730-24.861 with BAO 0.6-m Schmidt telescope under non-photometric weather. Combination of two relatively best quality 60-min. images taken with BATC band-i filter (central wavelength at 6660 A, band width 480 A) gives a detection of the object (OT+galaxy) at RA=15:25:30.17, Dec=+44:45:59.7 (J2000) with magnitude of 21.0 +/- 0.3 (Jan 24.818) using the No. 1 and No. 2 stars in GCN #204. No visual seperation between OT and galaxy could be recognized because of low S/N ratio and bad spatial resolution (1 pixel = 1.7", seeing = 5.6"). Central 4' X 4' part of the whole 58' X 58' CCD field will soon be available under http://vega.bac.pku.edu.cn/~zj/grb/grb990123.html Re-reduction of GCN #204 observation with only first 2 of the 4 stars gives same result for the OT+galaxy in magnitude of 19.2 +/- 0.1 (Jan 23.756). This report may be cited."