Data from five continuous years (1984 to 1989) at Teide Observatory (Iza na, Tenerife, Canary Islands) obtained with a full-disc solar multichannel photometer devoted to the detection of solar intensity oscillations has now been used for a detailed study of the extinction coefficient behaviour at several wavelengths (from 450 nm to 870 nm) and

Three different types of evidence are presented in favour of the hypothesis that the HII regions in disk galaxies with H-alpha luminosities greater than a critical value of 10^(38.6)^ erg s^(-1)^ are density bounded, and that the escaping Lyman continuum photons from these are the principal ionizing agents for the diffuse ISM in disk galaxies. This

IAUC 6875 available at Central Bureau for Astronomical Telegrams.

We present echelle spectroscopy in the 3500- to 7060-Å range for two positions of the Orion nebula. The data were obtained using the 2.1-m telescope at Observatorio Astrónmico Nacional in San Pedro Mártir, Baja California. We have measured the intensities of about 220 emission lines, in particular 81 permitted lines of C+, N+, N++, 0°, 0+, Ne0, Si+

We present optical and infrared observations of Roque Praesepe 1 (RPr 1), a faint ( I=21.01 ) and very red object ( I-K=4.57 ) discovered in a deep CCD survey, covering an area of 800 arcmin2 of the Praesepe open cluster. A low-resolution spectrum shows that RPr 1 is a very late object, the latest object in Praesepe for which a spectrum has been

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