Photopolarimetric observations in UBVRI bands and near-infrared photometric observations of the low polarization quasar 3C 273 obtained between February 1989 and May 1990 are presented. The degree of polarization remained low (below 1 percent) for most of the observing period and generally decreased toward shorter wavelengths. In early 1990

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Emission lines in the spectra of WC9 stars have been studied. It is shown that there are clear differences between the spectra of BD + 30 3639 and the central star of He2-99. It is argued that there are no systematic spectral differences between the WC9 CSPN and the Pop.I WC9 stars: both kinds of WC9 stars show a substantial and overlapping range

A list of 199 standard stars suitable for the ESO standard photometric system at JHKLM is given. Faint stars (although brighter than K = 7.7) to be used on larger telescopes are included. This list is based on an analysis of all infrared photometric observations carried out at La Silla from 1979 until 1989 inclusive. The accuracy of the data (about

We consider the compression of multispectral images using Hilbert scanning and adaptive arithmetic coding. The Hilbert scan is a general technique for continuous scanning of multidimensional data. Arithmetic coding has established itself as the superior method for lossless compression. The aim of this paper is to investigate the integration of the