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tokens: ratio of Y e = 0.30, for the assumed distance of 40 Mpc. We also present photometry of AT 2017gfo over a period 10 d post detection, in optical ( B, V and R ) and infrared ( J, H and K ), derived from the MASTER-SAAO and IRSF telescopes at Sutherland, respectively. We again compare these results to the respective kilonova model predictions, and conclude that either the Y e = 0.25 or 0.30 wind models are qualitatively similar to the observed magnitudes. 2 SALT AND SAAO OBSERVATIONS Following the detection of AT 2017gfo, the optical counterpart to GW170817, director’s discretionary time observations (programme 2017-1-DDT-009) were undertaken on 2017 August 18 and 19 on the Southern African Large Telescope (SALT; Buckley et al. 2006 ). The observations were taken with the prime focus Robert Stobie spectrograph (Burgh et al. 2003 ), beginning in twilight and proceeding until the end of the available telescope track time. A third attempt on August 20 resulted in no meaningful data being obtained due to the sky brightness coupled with the degree of fading of the kilonova. The observational details are included in Table 1 , and preliminary reports on the results are presented in Shara et al. ( 2017 ), Abbott et al. ( 2017b ), McCully et al. ( 2017 ) and Andreoni et al. ( 2017 ). Table 1. Observing details. Notes. a Transparency; seeing. b Since GW trigger time: 2017 August 17, 12h41m04s UTC. The low-resolution PG300 surface relief transmission grating was used, rotated to an angle of 5.75°, with a long slit of width 2 arcsec, which implies an ∼88 per cent slit throughput in the given seeing conditions. The spectra had a resolution which varied from R ∼ 150 (at ∼3750 Å) to ∼400 (at ∼9600 Å), with a mean of R ∼ 380. The observations were reduced using the PySALT package (Crawford et al. 2010 ), which accounts for basic CCD characteristics (cross-talk, bias and gain correction) and removal of cosmic rays, wavelength calibration, and relative flux calibration. Additional reductions to account for accurate sky and galaxy background removal were done using standard iraf routines. Because of the SALT design, which has a moving, field-dependent and underfilled entrance pupil, absolute flux calibration with SALT is difficult to achieve with a good degree of accuracy, which at best is ± 20 per cent. Observations were taken in morning twilight on 2017 August 18 of the spectrophotometric standard star EG21, which was used to determine a relative flux calibration on both nights. The spectral fluxes were then corrected by convolving the observed spectra with standard Johnson–Cousins B and R filters and comparing the results with B and R observations taken simultaneously with the MASTER-SAAO facility, which are included in Table 1 , corrected for Milky Way extinction, as presented in Lipunov et al. ( 2017 ). This comparison implied that the spectra were required to be adjusted in flux by a multiplicative constant of 2.04 and 2.4, respectively, on the