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tokens: in an unbroken sequence lasting for 9.45 h which is slightly longer than Ceres rotational period of 9.074 h. On August 26, we took a second sequence of 29 exposures of 900 s each. The observations started on August 26 at 23:36 ut at the beginning of the night and ended at the set of Ceres on August 27 at 06:49 UT ut (MJD 2457260.9878–2457261.2840) in an uninterrupted sequence lasting 7.25 h, i.e. a bit shorter than a complete rotation. Five exposures were also taken at the end of the night on August 27, when we could shortly open the dome during a pause of bad weather. The journal of the observations together with the relevant quantities are given in Table 1 which is available online. Table 1. Journal of July observations. 1 st column is the time of the start of the exposure in UT. 2 nd column is the time in MJD. 3 rd column is the radial velocity computed by the HARPS pipeline. 4 th column is the radial velocity corrected from the instrumental drift. 5 th column is the BERV of the HARPS pipeline. 6 th column is the exposure time in seconds. 7 th column is the flux weighted mid exposure fraction. 8 th column is the effective mid exposure time. 9 th column is the radial velocity of Ceres with respect to the Sun. 10 th is the radial velocity of the observer relative to Ceres. The full table is available online. Ceres had an APmag of ≈7.5 mag, an angular dimension of 0.69 arcsec and was observable during most of the night. The observations were performed at phase angles of 4.4 and 12.3 in July and August, respectively. At opposition, Ceres becomes slightly brighter due to the Opposition Surge effect, but no radial velocity variations are expected within a single rotational period (Molaro et al. 2015 ). Inspection of the solar activity through the Solar Dynamic Observatory revealed no significant change in the solar activity to induce an important radial velocity change. The solar activity measured from the total sunspot area changed slightly from ≈500 to ≈1250 millionths of solar hemisphere between July 31 July and August 27. However, note that these will introduce a radial velocity offset between the two nights but not a change within one epoch. We used HARPS pipeline to obtain the radial velocities from sunlight spectra which are reported in the third column of online Table 1 . In the HARPS spectrograph, a second fibre supplies simultaneous ThAr spectra that are used to correct for instrumental radial velocity drifts occurring over the night due to residual temperature, pressure or mechanical changes. The radial velocity differences with respect to the previous calibration provide the instrumental drifts of the spectrograph. We are considering the values RV c corrected for instrumental drift and reported in the column 4 of online Table 1 but note that corrections are always below 0.5 m s −1 and do not affect the results. Single observations have S/N ≥ 100 and the error in the radial velocity measurement is lower than 1 m s −1 .