Analysis of HH Tel. First column shows cleaned SW data folded according to epoch 2454347.2643 with the main pulsation period P = 0.4820925 d (top panel) and with the Blazhko period 133 d (middle panel). Frequency spectrum based on SW data in the vicinity of f₀ prewhitened with kf₀ is shown in the bottom panel in the first column. Second column displays the same as the first one but for the ASAS data. In the third column (based on SW data again), there are from the top changes in O−C values, changes of maximum brightness, and residuals after prewhitening with the main pulsation components at the bottom (epoch is shifted of a half of a period for better arrangement). For details see the text in Sect. 3.2.