Active optics control of VST telescope secondary mirror

Schipani, P.; D’Orsi, Sergio; Fierro, Davide; Marty, Laurent

doi:10.1364/ao.49.003199

Cited by 17 publications

(9 citation statements)

References 27 publications

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“…E. Iodice). The surveys were both performed with the ESO VLT Survey Telescope (VST), which is a 2.6 m diameter optical survey telescope located at Cerro Paranal, Chile (Schipani et al 2010). The imaging is in the u, g,r and i-bands using the 1 × 1 square degree field of view camera OmegaCAM (Kuijken 2011).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

The Fornax Deep Survey with VST

Cantiello

Venhola

Grado

et al. 2020

A&A

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Context. A possible pathway for understanding the events and the mechanisms involved in galaxy formation and evolution is an in-depth investigation of the galactic and inter-galactic fossil sub-structures with long dynamical timescales: stars in the field and in stellar clusters. Aims. This paper continues the Fornax Deep Survey (FDS) series. Following previous studies dedicated to extended Fornax cluster members, we present the catalogs of compact stellar systems in the Fornax cluster, as well as extended background sources and point-like sources. Methods. We derived ugri photometry of ∼1.7 million sources over the ∼21 square degree area of FDS centered on the bright central galaxy NGC 1399. For a wider area, of ∼27 square degrees extending in the direction of NGC 1316, we provided gri photometry for ∼3.1 million sources. To improve the morphological characterization of sources, we generated multi-band image stacks by coadding the best-seeing gri-band single exposures with a cut at full width at half maximum (FWHM) ≤ 0.″9. We used the multi-band stacks as master detection frames, with a FWHM improved by ∼15% and a FWHM variability from field to field reduced by a factor of ∼2.5 compared to the pass-band with the best FWHM, namely the r-band. The identification of compact sources, in particular, globular clusters (GC), was obtained from a combination of photometric (e.g., colors, magnitudes) and morphometric (e.g., concentration index, elongation, effective radius) selection criteria, also taking as reference the properties of sources with well-defined classifications from spectroscopic or high-resolution imaging data. Results. Using the FDS catalogs, we present a preliminary analysis of GC distributions in the Fornax area. The study confirms and extends further previous results that were limited to a smaller survey area. We observed the inter-galactic population of GCs, a population of mainly blue GCs centered on NGC 1399, extending over ∼0.9 Mpc, with an ellipticity ϵ ∼ 0.65 and a small tilt in the direction of NGC 1336. Several sub-structures extend over ∼0.5 Mpc along various directions. Two of these structures do not cross any bright galaxy; one of them appears to be connected to NGC 1404, a bright galaxy close to the cluster core and particularly poor in GCs. Using the gri catalogs, we analyze the GC distribution over the extended FDS area and do not find any obvious GC sub-structure bridging the two brightest cluster galaxies, namely, NGC 1316 and NGC 1399. Although NGC 1316 is more than twice as bright of NGC 1399 in optical bands, using gri data, we estimate a GC population that is richer by a factor of ∼3−4 around NGC 1399, as compared to NGC 1316, out to galactocentric distances of ∼40′ or ∼230 kpc.

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Section: Observations and Data Reductionmentioning

confidence: 99%

The Fornax Deep Survey with VST

Cantiello

Venhola

Grado

et al. 2020

A&A

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“…It can be tilted for alignment purposes by modifying the positions of three fixed points on the third ring at angles of 120°. The rigid-body position of the convex hyperbolic secondary mirror can be controlled by a hexapod in 5 degrees of freedom [16]. Strictly speaking, the VST does not belong to any classical category of telescopes (e.g., Cassegrain, Ritchey-Chretien): the combination of mirrors and lenses has been designed in order to minimize the wavefront error across the whole field of view.…”

Section: Telescope Overviewmentioning

confidence: 99%

Removing static aberrations from the active optics system of a wide-field telescope

et al. 2012

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The wavefront sensor in active and adaptive telescopes is usually not in the optical path toward the scientific detector. It may generate additional wavefront aberrations, which have to be separated from the errors due to the telescope optics. The aberrations that are not rotationally symmetric can be disentangled from the telescope aberrations by a series of measurements taken in the center of the field, with the wavefront sensor at different orientation angles with respect to the focal plane. This method has been applied at the VLT Survey Telescope on the ESO Paranal observatory.

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“…All major ground-based telescopes use some form of adaptive optics to correct for atmospheric turbulence, usually with additional optics beyond the telescope [11]. The past 15 years have seen the development of active primary and secondary mirrors, where aberrations are corrected within the telescope itself to eliminate the need for additional optics.…”

Section: Active Secondary Mirrormentioning

confidence: 99%

Actuation for carbon fiber reinforced polymer active optical mirrors

Jungwirth

Wick

Baker³

et al. 2012

2012 IEEE Aerospace Conference

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Adaptive or active elements can alter their shape to remove aberrations or shift focal points. Carbon fiber reinforced polymer (CFRP) material improves upon current active mirror materials, such as Zerodur, in several ways: low stiffness-to-weight ratio, very low hysteresis, and greater dynamic range of correction. In this paper, we present recent developments in CFRP mirror actuation, i.e., changing the mirror's shape in an accurate and repeatable fashion. Actuation methods are studied both theoretically, using finite element analysis, and experimentally, using interferometric testing. We present results using two annular rings to push against the mirror's back, producing a wavefront with less than 20 waves of total error. Applications for this work include active telescope secondaries, phase diversity, and adaptive zoom systems.

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Active optics control of VST telescope secondary mirror

Cited by 17 publications

References 27 publications

The Fornax Deep Survey with VST

The Fornax Deep Survey with VST

Removing static aberrations from the active optics system of a wide-field telescope

Actuation for carbon fiber reinforced polymer active optical mirrors

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