TITLE: GCN CIRCULAR NUMBER: 21300 SUBJECT: GRB 170705A: ISON/Terskol optical observations DATE: 17/07/06 13:28:01 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Pozanenko (IKI), V. Agletdinov (KIAM), A. Volnova (IKI), A. Mokhnatkin (KIAM), I. Molotov (KIAM) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 170705A (Starling et al. GCN 21289) which is also detected by GBM/Fermi and Konus-Wind (Bissaldi et al., GCN 21297; Svinkini et al., GCN 21299) with K-800 (0.8m) telescope of ISON/Terskol observatory starting on July, 05 (UT) 18:30:54. We obtained several unfiltered images of 20 s exposure. The optical afterglow of GRB 170705A (Starling et al. GCN 21289, Lipunov et al. GCN 21291, Butler et al. GCN 21293, Emery et al. GCN 21294; Ugarte Postigo et al. GCN 21298) is clearly visible in a combined image. Preliminary photometry of the afterglow is following Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2017-07-05 18:30:54 0.70649 CR 358*20 19.84 0.08 22.2 Photometry is based on nearby SDSS DR9 stars SDSS id R_Lupton J124702.82+181926.7 17.63 J124700.96+181851.9 19.15 J124653.35+182058.9 17.08 J124641.28+182043.7 16.61 J124646.57+181522.1 17.45 J124645.71+181510.4 17.18 J124650.58+182306.3 18.18 J124624.60+181820.0 16.34 J124647.75+181330.6 16.05 J124644.99+181414.3 18.79