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16 papers found.
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Site testing at astronomical sites: evaluation of seeing using satellite-based data

. Cavazzani S. , Ortolani S. , Zitelli V. , Maruccia Y. , 2011 , MNRAS, 411 , 1271 Della Valle A. , Maruccia Y. , Ortolani S. , Zitelli V. , 2010 , MNRAS, 401 , 1904 (Paper III ) Erasmus D. , Sarazin M. , 2002

Fluctuations of photon arrival times in free atmosphere

In this paper we calculate the delay of the arrival times of visible photons on the focal plane of a telescope and its fluctuations as a function of local atmospheric conditions (temperature, pressure, chemical composition, seeing values) and telescope diameter. The aim of this paper is to provide a model for delay-time fluctuations accurate to the picosecond level, as required by ...

The astroclimatological comparison of the Paranal Observatory and El Roque de Los Muchachos Observatory

The new extremely large telescope projects need accurate evaluation of the candidate sites. In this paper, we present the astroclimatological comparison between the Paranal Observatory, located on the coast of the Atacama Desert (Chile), and the Observatorio del Roque de Los Muchachos (ORM), located in La Palma (Canary Islands). We apply a statistical analysis using long-term data ...

Fraction of clear skies above astronomical sites: a new analysis from the GOES12 satellite

Comparing the number of clear (cloud-free) nights available for astronomical observations is a critical task, which should be based on homogeneous methodologies. Current data are mainly based on different judgements based on observer logbooks or on different instruments. In this paper, we present a new homogeneous methodology at very different astronomical sites for modern optical ...

TNG DIMM working on Roque de los Muchachos

Since 2011 February 27 a new differential image motion monitor (DIMM) has been operating at Roque de los Muchachos Observatory close to the Telescopio Nazionale Galileo (TNG). The purpose of this instrument is to provide useful information about the optical turbulence for astronomical observations in the neighbourhood of the TNG. We present the first statistical results from it as ...

The old metal-poor open cluster ESO 92-SC05: accreted from a dwarf galaxy?

S. Ortolani E. Bica B. Barbuy 0 Universidade de Sa o Paulo , Rua do Mata o 1226, 05508-900 Sa o Paulo , Brazil 1 Universidade Federal do Rio Grande do Sul , Dept de Astronomia, CP 15051, Porto Alegre

Open cluster survival within the solar circle: Teutsch 145 and Teutsch 146*

Teutsch 145 and Teutsch 146 are shown to be open clusters (OCs) orbiting well inside the solar circle, a region where several dynamical processes combine to disrupt most OCs on a time-scale of a few 108 yr. BVI photometry from the GALILEO telescope is used to investigate the nature and derive the fundamental and structural parameters of the optically faint and poorly known OCs ...

Near-infrared thermal emissivity from ground-based atmospheric dust measurements at ORM*

We present an analysis of the atmospheric content of aerosols measured at Observatorio del Roque de los Muchachos (ORM; Canary Islands). Using a laser diode particle counter located at the Telescopio Nazionale Galileo (TNG) we have detected particles of 0.3, 0.5, 1.0, 3.0, 5.0 and 10.0 μm size. The seasonal behaviour of the dust content in the atmosphere is calculated. Spring has ...

Analysis of the fraction of clear sky at the La Palma and Mt Graham sites

The amount of available telescope time is one of the most important requirements when selecting astronomical sites, as it affects the performance of ground-based telescopes. We present a quantitative survey of cloud coverage at La Palma and Mt Graham using both ground- and satellite-based data. The aim of this work is to derive clear nights for the satellite infrared channels and ...

Multi-Conjugate Adaptive Optics VLT imaging of the distant old open cluster FSR 1415

We employ the recently installed near-infrared Multi-Conjugate Adaptive Optics demonstrator (MAD) to determine the basic properties of a newly identified, old and distant, Galactic open cluster (FSR 1415). The MAD facility remarkably approaches the diffraction limit, reaching a resolution of 0.07 arcsec (in K), that is also uniform in a field of ∼1.8 arcmin in diameter. The MAD ...

Astronomical site selection: on the use of satellite data for aerosol content monitoring

The main goal of this work is to analyse new approaches to the study of the properties of astronomical sites. In particular, satellite data measuring aerosols have recently been proposed as a useful technique for site characterization and searching for new sites to host future very large telescopes. Nevertheless, these data need to be critically considered and interpreted in ...

Effects of long-term strontium ranelate treatment on vertebral fracture risk in postmenopausal women with osteoporosis

Jimnez Diaz, Avenida de los Reyes Catolicos, 28040 Madrid, Spain 12 S. Ortolani Divisione di Endocrinologia, Istituto Auxologico Italiano , Via Ariosto, 13, 20145 Milan, Italy Summary Vertebral fractures

A pair of reddened young star clusters in Centaurus

Photometry in the BVI and JHK bands is presented for the first time for the southern open clusters Danks 1 and 2, located in the Centaurus region. They are relatively rich and compact, and projected at approximately 4 arcmin from each other. The clusters are very reddened, with AV= 8.1 ± 0.45 and 9.3 ± 0.6, respectively. They are young clusters, with ages of approximately 10 Myr, ...

HP 1: a blue horizontal branch globular cluster in the bulge

We present V, I colour-magnitude diagrams of the globular cluster HP 1 obtained at the European Southern Observatory New Technology Telescope under exceptional seeing conditions. The cluster shows blue horizontal branch (HB) and red giant branch morphologies very similar to clusters of intermediate metallicity such as NGC 6752; we therefore estimate [Fe/H] ≈ − 1.5 for HP 1. The ...

NGC 6749: a metal-poor halo globular cluster in a disc field rich in Mira variables

L. Rosino/ S. Ortolani 1 B. Barbuf E. Bica 3 0 Universidade de Siio Paulo , lAG, Dept de Astronomia, CP 9638, Siio Paulo 01065-970, Brazil 1 Universitii di Padova , Dept di Astronomia, Vicolo

The luminosity function of the globular cluster NGC 6752 with the Hubble Space Telescope: evidence of mass segregation

We present the luminosity function (LF) for the lower main sequence of the Galactic globular cluster NGC 6752, as obtained from Hubble Space Telescope (HST) observations centred 2 arcmin from the cluster centre. We present data in the F814W and F555W filters. Our LF reaches down to M1 = 11 or, translated to a mass function, to M≃0.12 M⊙. The LF reaches a maximum between M1 = 8.5 ...