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Spectral indices (delta m2100 and delta m1500) for 32 O-type stars with known spectral class and reddening are plotted versus log of effective temperature. The delta m2100 indices are considered to be almost luminosity-independent, while evidence of a well-established relationship between observed spectral indices and empirical temperatures appears

The software package ELSPEC/1 written at Trieste Astronomical Observatory for the automatic reduction of spectrograms digitized by a PDS 1010A microdensitometer is described and an example of the results obtained is shown. The package accepts spectrograms in the format of the Observatoire de Hauts Provence and operates on a HP 2100A minicomputer.

A brief description is given of the IMAGE-1 software package for the presentation and evaluation of digitized images at the Osservatorio Astronomico di Trieste. The package makes it possible to draw isophotes in an interactive way and to have an assonometric display of the image studied.

Results of almost simultaneous observations of the differential rotation of the Ca(plus) chromosphere and the photospheric plasma are reported. The observations (tracings of Ca(plus) mottles and Doppler shift measurements in a photospheric line) were performed at the Locarno station during two extended periods in 1976. Both data sets were used to

Using a resonant scattering spectrometer, observations of integral solar light have been recorded and analyzed to determine the existence of solar oscillations. Although the data from individual days do confirm the existence of long-period oscillations, these do not seem to be consistent in either period, amplitude or phase. Possible interpretation