75 research outputs found
Characterization of a Double Mesospheric Bore Over Europe
Observations of a pair of mesospheric bore disturbances that propagated through the nighttime mesosphere over Europe are presented. The observations were made at the Padua Observatory, Asiago (45.9\ub0N, 11.5\ub0E), by the Boston University all-sky imager on 11 March 2013. The bores appeared over the northwest horizon, approximately 30 min apart, and propagated toward the southeast. Using additional satellite and radar data, we present evidence indicating the bores originated in the mesosphere from a single, larger-scale mesospheric disturbance propagating through the mesopause region. Furthermore, the large-scale mesospheric disturbance appeared to be associated with an intense weather disturbance that moved southeastward over the United Kingdom and western Europe during 10 and 11 March
FrogEye, the Quantum Coronagraphic mask. The Photon Orbital Angular Momentum and its applications to Astronomy
We propose to realize an optical device based on the properties of photon
orbital angular momentum (POAM) to detect the presence of closeby faint
companions in double systems using Laguerre-Gaussian (L-G) modes of the light.
We test also the possibility of using L-G modes to build coronagraph mask. We
realized in the laboratory a prototype using a blazed l=1 hologram to simulate
the separation between two stars, as observed with a telescope, in
Laguerre-Gaussian modes.Comment: 2 pages, XLIX meeting of the Italian Astronomical Society (SAIT
Recovering pyramid WS gain in non-common path aberration correction mode via deformable lens
It is by now well known that pyramid based wavefront sensors, once in closed
loop, have the capability to improve more and more the gain as the reference
natural star image size is getting smaller on the pyramid pin. Especially in
extreme adaptive optics applications, in order to correct the non-common path
aberrations between the scientific and sensing channel, it is common use to
inject a certain amount of offset wavefront deformation into the DM(s),
departing at the same time the pyramid from the optimal working condition. In
this paper we elaborate on the possibility to correct the low order non-common
path aberrations at the pyramid wavefront sensor level by means of an adaptive
refractive lens placed on the optical path before the pyramid itself, allowing
the mitigation of the gain loss
Overcoming the Rayleigh Criterion Limit with Optical Vortices
We experimentally and numerically tested the separability of two independent
equally-luminous monochromatic and white light sources at the diffraction
limit, using Optical Vortices (OV), related to the Orbital Angular Momentum
(OAM) of light. The diffraction pattern of one of the two sources crosses a
phase modifying device (fork-hologram) on its center generating the
Laguerre-Gaussian (L-G) transform of an Airy disk. The second source, crossing
the fork-hologram in positions different from the optical center, acquires
different OAM values and generates non-symmetric L-G patterns. We formulated a
criterion, based on the asymmetric intensity distribution of the superposed L-G
patterns so created, to resolve the two sources at angular distances much below
the Rayleigh criterion. Analogous experiments carried out in white light allow
angular resolutions which are still one order of magnitude below the Rayleigh
criterion. The use OVs might offer new applications for stellar separation in
future space experiments.Comment: 4 pages, 5 figure
(Very) Fast astronomical photometry for meter-class telescopes
Our team at the INAF-Astronomical Observatory of Padova and the University of Padova is engaged in the design, construction and operations of instruments with very high time accuracy in the optical band for applications to High Time Resolution Astrophysics and Quantum Astronomy. Two instruments were built to perform photon counting with sub-nanosecond temporal accuracy, Aqueye+ and Iqueye. Aqueye+ is regularly mounted at the 1.8m Copernicus telescope in Asiago, while Iqueye was mounted at several 4m class telescopes around the world and is now attached through the Iqueye Fiber Interface to the 1.2m Galileo telescope in Asiago. They are used to perform coordinated high time resolution optical observations and, for the first time ever, experiments of optical intensity interferometry on a baseline of a few kilometers. We report on recent technological developments and scientific results obtained within the framework of this project...
Optical vortices with starlight: Implications for ground-based stellar coronagraphy
Using an l = 1 blazed fork-hologram at the focal plane of the Asiago 122 cm
telescope, we obtained optical vortices from the stellar system Rasalgethi
(alpha Herculis) and from the single star Arcturus (alpha Bootis). We have
analyzed the structure of the optical vortices obtained from non-monochromatic
starlight under very poor seeing conditions using a fast CCD camera to obtain
speckle patterns and carry out the lucky imaging technique, alternative to
adaptive optics. With the insertion of a red filter and of a Lyot stop we
performed l = 1 optical vortex coronography the double star HD74010. The
results are in agreement with theory and numerical simulations. Our results
open the way to applications of optical vortices to ground based astronomical
observations, in particular for coronagraphy with l > 1 masks. No intrinsic
orbital angular momentum was detected in the starlight.Comment: 4 pages, 5 figures. Revised data analysi
VST: the telescope progress toward stars
The VST telescope is in an advanced stage of integration in Chile, after a period of work spent mainly on the active optics system, started in mid-2007. We present the results of the recent work on the primary and secondary mirror support systems and on the mirror cell auxiliary units
Data processing on simulated data for SHARK-NIR
A robust post processing technique is mandatory to analyse the coronagraphic
high contrast imaging data. Angular Differential Imaging (ADI) and Principal
Component Analysis (PCA) are the most used approaches to suppress the
quasi-static structure in the Point Spread Function (PSF) in order to revealing
planets at different separations from the host star. The focus of this work is
to apply these two data reduction techniques to obtain the best limit detection
for each coronagraphic setting that has been simulated for the SHARK-NIR, a
coronagraphic camera that will be implemented at the Large Binocular Telescope
(LBT). We investigated different seeing conditions () for stellar
magnitude ranging from R=6 to R=14, with particular care in finding the best
compromise between quasi-static speckle subtraction and planet detection.Comment: 9 pages, 8 figures, proceeding for the fifth Adaptive Optics for
Extremely Large Telescopes (AO4ELT5) meeting in 201
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