Chopping between the source and 1 or 2 background positions was an ISOPHOT observing mode for faint source photometry. More than 7000 observations of this type were performed during the mission. We review the main instrumental effects related to chopping, and describe the data reduction steps and calibration strategies developed for this mode. A

It is known that the convective motions at solar photosphere level are visible in the frequency domain through the so called ""solar noise"". Time-resolved differential CCD photometry time series form 2 to 4 days long obtained at the Observatorio del Teide Izaña (Tenerife) using the 1m telescope of the Optical Ground Station (OGS) have been taken

The OSIRIS Tunable Emission Line Object survey (OTELO) will provide a deep, complete sample of active galactic nuclei (AGN), and able to separate them accurately from nuclear star forming galaxies based on line strength ratios. The OTELO survey will be able to address several still open questions about the nature of AGN and their host galaxies.

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A pilot experiment suitable to test Newton's law of gravity down to the regime of acceleration typical of galaxies has been carried out in Omega Centauri. Stars in the extreme periphery of this globular cluster are used as test particles immersed in such weak gravitational field. The stellar velocity dispersion is found to remain constant at large

We report the results of an HST survey of 17 AGN, selected solely for having a well developed radio jet bright enough to be detectable with HST for a normal radio-to-optical spectral index. It is found that optical jets are much more common then expected, been detected in ˜30% of the cases. The data are then combined with Chandra X-ray and VLA