Transit timing residuals versus the linear ephemeris of Eq. (3). The filled symbols represent the two transits of H11 and the transit of this work, which were used to derive the ephemeris. The open symbols show the amateur ETD transits. The dotted lines give the 1σ uncertainty of the ephemeris as a function of cycle number. The dashed line shows the difference when the amateur data are included in the ephemeris fit, which yielded no significant improvement and was finally not used for Eq. (3).