The total solar irradiation (TSI) is the primary quantity of energy that is provided to the Earth. The properties of the TSI variability are critical for understanding the cause of the irradiation variability and its expected influence on climate variations. A deterministic property of TSI variability can provide information about future irradiation variability and expected long-term climate variation, whereas the non-deterministic variability can only explain the past. This study of solar variability is based on an analysis of the TSI data series from 1700 A.D. and 1000 A.D., a sunspot data series from 1611 A.D., and a solar orbit data series from 1000 A.D. The study is based on a wavelet spectrum analysis. First the TSI data series are transformed into a wavelet spectrum. Then the wavelet spectrum is transformed into an autocorrelation spectrum, to identify stationary, subharmonic and coincidence periods in the TSI variability. The results indicate that the TSI and sunspot data series have periodic cycles that is correlated to the solar position oscillation and controlled by gravity force variations from the large planets Jupiter, Saturn, Uranus and Neptune and the solar dynamo. A possible explanation is forced oscillations between the large

Account of the extinction in the Earth’s atmosphere is an important part of the WET light curve reduction procedures. Usually, WET observations are not corrected for the second order extinction effects: the dependence of the extinction coefficient on spectral type and on air mass (the Forbes effect). The ignorance of these effects does not change seriously the derived pulsation amplitudes at the frequencies higher than 200 μHz but the increase of the noise at lower frequencies takes place. For obtaining the true extra-atmospheric magnitudes of stars, a modification of the extinction correction procedure is proposed. For photometry with the R647 phototube we recommend to use a filter cutting out the region below 310 nm, in order to decrease and stabilize the extinction coefficient. A method for estimation of spectral type of the comparison star from WET observations is proposed.