A method for applying a modified Wiener filter to time-tagged single photon data is proposed which can preprocess the data for use by a wide range of image sharpening algorithms. The method is applied to data from the 50-cm Roque de los Muchachos Observatory telescope, resulting in near diffraction limited images of the bright triple-star system

The effect produced by a sharp discontinuity in the upper boundary of the conductosphere is analysed in order to evaluate the distortions introduced in geomagnetic variation profiles in the long-period range of the spectra. To do so, a conformal mapping method is applied and the results are compared with the ones obtained in the case of lateral

Infrared observations are used to obtain effective temperatures with a 3-percent error for a sample of low main-sequence stars. The empirical calibration of Arribas and Martinez Roger (1988) is found to be valid except for the lowest metallicities and for effective temperatures of lower than 5000 K, and to predict exceedingly blue colors for solar

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Results are presented on optical and near-IR photometry of cometary nebula 1548 C27, together with associated high and intermediate resolution spectroscopy of both the nebular core and jet outflow. Two IR sources were found, one of which, IRS 2, is clearly a reddened main-sequence star, the other, IRS 1, being a probable Herbig Ae/Be type central

The influence of general relativistic effects on spectral line profiles is studied. Some peculiarities observed in the profiles of broad lines of AGNs, like the global redshift of the line and simultaneous blueshift of the peak of the profile with respect to the reference system of the narrow lines, are obtainable if the source region is rotating