Temporal evolution of the Fried-parameter r₀ (black dots) and air mass (solid line) during the 16 July 2023 observations with the 1.5-metre Gregor solar telescope. The light grey rectangle corresponds to the time interval of the HiFI+ observations. The black dots were taken from the Gregor status monitor and the colour-coded dots are recorded in the headers of the GRIS scans. The colour-coded dots refer to the Fried-parameter r₀ for each step during the five GRIS scans. The air mass was obtained by using the web interface to the JPL Horizons On−Line Ephemeris System.