We present a detailed photometric study of the dwarf irregular galaxy NGC 6822 aimed at investigating the properties of its stellar populations and, in particular, the presence of stellar radial gradients. Our goal is to analyse the stellar populations in six fields, which cover the whole bar of this dwarf galaxy. We derived the quantitative star

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.

We report Hubble Space Telescope observations of six gravitational lenses with the Advanced Camera for Surveys. We measured the flux ratios between the lensed images in seven filters from 8140 Å to 2200 Å. In three of the systems, HE0512-3329, B1600+434, and H1413+117, we were able to construct UV extinction curves partially overlapping the 2175 Å

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We present the first deep, optical, wide-field imaging survey of the young open cluster Collinder 359, complemented by near-infrared follow-up observations. This study is part of a large programme aimed at examining the dependence of the mass function on environment and time. We have surveyed 1.6 square degree in the cluster in the I and z filters

We present new high-resolution near-infrared observations in the J, H, and K bands, obtained to study the properties of Seyfert host galaxies. The data set consists of images in the three bands of practically the entire CfA sample of Seyfert galaxies, and K-band images of a control sample of nonactive, ``normal,'' galaxies, matched to the Seyfert