Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA.

The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. ?? 2013 Elsevier B.V. All rights reserved

International audienceWe present relative astrometric measurements of visual binaries made during the second semester of 2005, with the speckle camera PISCO at the 102 cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. The purpose of this long term program is to improve the accuracy of the orbits and determine the masses of the components.\ We performed 130 new observations of 120 objects, with most of the angular separations in the range 0\farcs1-4\arcsec, and with an average accuracy of 0\farcs01. Most of the position angles could be determined without the usual 180° ambiguity with the application of triple-correlation techniques, and their mean error is 0\fdg8. We have found a possible new triple system: ADS 11077. ?kip0.15cm The measurements of the closest binaries were made with a new data reduction procedure, based on model fitting of the background of the auto-correlations. As this procedure proved to be very efficient, we have re-processed the old observations of close binaries made with PISCO in Merate since 2004. We thus improved 20 measurements already published and obtained 7 new measurements for observations that were previously reported as ``unresolved".\ We finally present revised orbits for ADS 684, MCA 55Aac (in the Beta 1 Cyg-Albireo multiple system) and ADS 14783 for which the previously published orbits led to large residuals with our measurements and for which the new observations made since their computation allowed a significant improvement of those old orbits. The sum of the masses that we derived for those systems are consistent with the spectral type of the stars and the dynamic parallaxes are in good agreement with the parallaxes measured by Hipparcos

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We present relative astrometric measurements of visual binaries made with the Pupil Interferometry Speckle camera and Coronagraph (PISCO) at the 1‐m Zeiss telescope of Brera Astronomical Observatory, in Merate. We provide 135 new observations of 103 objects, with angular separations in the range 0.1–4.0 arcsec and with an accuracy better than ∼0.01 arcsec. Our sample is made of orbital couples as well as binaries whose motion is still uncertain. Our purpose is to improve the accuracy of the orbits and constrain the masses of the components. This work already leads to the revision of the orbits of three systems (ADS 5447, 8035 and 8739).