Data obtained at the Observatorio del Teide (Tenerife) during the years 1978 to 1988 using a resonant scattering spectrophotometer, is analyzed to look for variations of the low degree p-mode frequencies along the solar cycle. The analysis based on the cross-correlation of power spectra suggests that the variation of its maximum correlation

Effects of differential extinction across the Earth's atmosphere on astronomical photometry are reviewed. Under the same circumstances when a rotating extended object is observed spectrometrically, a residual radial velocity is obtained which varies during the day. In the case of integral sunlight observations, this effect was calculated along the

The question of whether or not solar g-modes can be detected and identified from ground observations is addressed. The limitation imposed by the Earth's atmosphere, the background solar noise spectrum at low frequencies, and a poor theoretical knowledge of these modes are mentioned. Using the best uninterrupted full disk velocity measurements

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On a recent spectrogram of the planetary nebula NGC 6572 the authors have found He II 4686 clearly in emission. They review previous descriptions of the spectrum and conclude that He II 4686 is stronger than 20 years ago. They briefly discuss the possible implications of this result, and suggest a careful monitoring of several planetary nebulae.

The Variability of solar IRradiance and Gravity Oscillations (VIRGO) experiment contains two types of active cavity radiometers for monitoring of the solar constant, two three channel sunphotometers for the measurement of spectral irradiance at 335, 500 and 865 nm and a low resolution imager with 12 pixels. The main scientific objective is probing