Tomographic control for wide field AO systems on extremely large telescopes

2010 ◽  
Author(s):  
C. Petit ◽  
J.-M. Conan ◽  
T. Fusco ◽  
B. Neichel
Keyword(s):  
Wide Field ◽  
Large Telescopes

scholarly journals Active optics in astronomy – modeling of deformable substrates: freeform surfaces for FIREBall and MESSIER

2018 ◽  
Vol 27 (5-6) ◽  
Author(s):  
Gérard Rene Lemaitre
Keyword(s):  
Adaptive Optics ◽  
Large Scale ◽  
Wide Field ◽  
Freeform Surfaces ◽  
Aspheric Surfaces ◽  
Massive Black Holes ◽  
Active Optics ◽  
Minimum Number ◽  
Co Addition ◽  
Large Telescopes

AbstractActive optics techniques on large telescopes and astronomical instrumentations provide high imaging quality. For ground-based astronomy, the co-addition of adaptive optics again increases angular resolution up to providing diffraction-limited imaging at least in the infrared. Active and adaptive optics marked milestone progress in the detection of exoplanets, super-massive black holes, and large-scale structure of galaxies. This paper is dedicated to highly deformable active optics that can generate non-axisymmetric aspheric surfaces – or freeform surfaces – by use of a minimum number of actuators: a single uniform load acts over the surface of a vase-form substrate whilst under reaction to its elliptical perimeter ring. Two such instruments are presented: (1) the Faint Intergalactic Redshifted Emission Balloon (FIREBall) telescope and multi object spectrograph (MOS) where the freeform reflective diffraction grating is generated by replication of a deformable master grating, and (2) the MESSIER wide-field low-central-obstruction three-mirror-anastigmat (TMA) telescope proposal where the freeform mirror is generated by stress figuring and elastic relaxation. Freeform surfaces were obtained by plane super-polishing. Preliminary analysis required use of the optics theory of 3rd-order aberrations and elasticity theory of thin elliptical plates. Final cross-optimizations were carried out with Zemax raytracing code and Nastran FEA elasticity code in order to determine geometry of the deformable substrates.

scholarly journals Imaging Spectroscopy on Very Large Telescopes

1984 ◽  
Vol 79 ◽  
pp. 515-517
Author(s):  
Paul Atherton
Keyword(s):  
Fourier Transform ◽  
Spatial Information ◽  
Broad Band ◽  
Imaging Spectroscopy ◽  
Wide Field ◽  
Two Dimensional ◽  
Imaging Spectrometer ◽  
Resolution Element ◽  
Fabry Perot ◽  
Large Telescopes

Imaging Spectroscopy is a technique in which a spectrum is obtained for each spatial resolution element across a wide field. The data is essentially 3-D, and may be viewed as a series of monochromatic images, or as a two dimensional array of spectra. A device generating such data may be called an imaging spectrometer. In a previous paper (Atherton, 1983 SPIE 445, 535) three different imaging spectrometers - based on grating, Fabry-Perot and Fourier Transform devices - were compared in terms of their ability to obtain spectral and spatial information over a wide field and broad band, to the same spectral resolution and S/N ratio, using the same detector array. From such a study it is clear that interferometer based devices are significantly faster than conventional grating spectrographs.

scholarly journals Advanced Wide-Field Broad-Passband Refracting Field Correctors for Large Telescopes

1984 ◽  
Vol 79 ◽  
pp. 519-548 ◽  
Author(s):  
H.W. Epps ◽  
J.R.P. Angel ◽  
E. Anderson
Keyword(s):  
Image Quality ◽  
Atmospheric Dispersion ◽  
Wide Field ◽  
Atmospheric Refraction ◽  
Optical Elements ◽  
Large Telescopes ◽  
The University ◽  
Near Future ◽  
Optical Manufacturing ◽  
Made In

AbstractA preliminary 30-arcmin prime focus (f/2.0) refracting field corrector system for the University of California Ten-Meter Telescope (UC TMT) is presented which features 1/4-arcsec images containing more than 80% of the energy, over limited passbands within the wavelength range λ3300Å to λ1.0µ. Provision has been made in this system for an atmospheric dispersion corrector (ADC) but same has not yet been realized. Optical elements herein are small enough that this design could be scaled up to a Fifteen-Meter NNTT/SMT.A compact 40-arcmin internal Cassegrain (f/1.75 hyperbola to f/5.0) broad-passband (λ3300Å to λ1.0µ) corrector, suitable for imaging and multi-object spectroscopy at the UC TMT, is presented which features 1/4-arcsec images containing more than 90% of the energy when averaged over field angle and color.Three 60-arcmin external Cassegrain correctors for 300-inch f/1.8 and f/2.0 parabolic primary mirrors are presented which are suitable for a Fifteen-Meter NNTT/MMT. Image quality is comparable to the UC TMT Cassegrain corrector and it exceeds that of the UC TMT preliminary prime focus corrector system by a substantial margin. Each of these correctors contains an ADC which has been implemented in one example, eliminating 4.0 arcsec of differential atmospheric refraction with an rms residual of +/-0.10 arcsec over the broad passband (λ3300Å to λ1.0µ). A 60-arcmin external Cassegrain (f/1.8 extreme hyperbola to f/4.5) corrector with ADC yields yet a factor two in image quality but said hyperbolic primary mirror would be incompatible with angular field requirements in the thermal infrared.A (300-inch) 40-arcmin external Cassegrain (f/1.0 parabola to f/4.0) broad-passband (λ3300Å to λ1.0µ) corrector with ADC is presented. Image quality is comparable to the previous Cassegrain correctors. The practicality of this design, together with recent advances in optical manufacturing capability of large, fast, nonspherical optics, suggests that relatively inexpensive compact telescopes of very large collecting area may be possible in the near future.

scholarly journals A New Type of Atmospheric Dispersion Corrector Suitable for Wide-Field High-Resolution Imaging and Spectroscopy on Large Telescopes

2021 ◽  
Vol 11 (14) ◽  
pp. 6261
Author(s):  
Andrew Rakich
Keyword(s):  
High Resolution ◽  
Atmospheric Dispersion ◽  
Wide Field ◽  
High Resolution Imaging ◽  
Dispersion Correction ◽  
Atmospheric Effect ◽  
New Type ◽  
Resolution Imaging ◽  
Imaging And Spectroscopy ◽  
Large Telescopes

Atmospheric dispersion produces spectral elongation in images formed by land-based astronomical telescopes, and this elongation increases as the telescope points away from the zenith. Atmospheric Dispersion Correctors (ADCs) produce compensating dispersion that can be adjusted to best cancel out the atmospheric effect. These correctors are generally of two basic types: Rotating Atmospheric Dispersion Correctors (R-ADCs), and Linear Atmospheric Dispersion Correctors (L-ADCs). Lately, a third type, the “Compensating Lateral ADC” (CL-ADC) has been proposed. None of these design approaches allow for large corrector systems (with elements greater than 1 m in diameter), in which the secondary spectrum is corrected to small residuals, of the order of tens’ of milliarcseconds. This paper describes a new type of large corrector (>1 m diameter elements), which can achieve the correction of the secondary spectrum to the order of 10 milliarcseconds. This correction is achieved by combining the R-ADC and CL-ADC approaches to dispersion correction. Only glass types readily available in metre diameters are required.

scholarly journals Lightweight cylindrical composite shell structures to support optical instruments in extremely large telescopes: A case study

2021 ◽  
Vol 104 (3) ◽  
pp. 003685042110361
Author(s):  
Lingyu Zheng ◽  
Daxu Zhang ◽  
Long Wang ◽  
Aman Shrestha ◽  
Zhensen Song ◽  
...  
Keyword(s):  
Fundamental Frequency ◽  
Shell Structure ◽  
Composite Shell ◽  
Wide Field ◽  
Maximum Displacement ◽  
Optical Instruments ◽  
Before And After ◽  
Cylindrical Composite Shell ◽  
Large Telescopes ◽  
Composite Shell Structure

Aiming at the issues of heavy weight and insufficient structural performance of optical instrument supporting structures in extremely large telescopes, the Wide-Field Optical Spectrograph (WFOS) of the Thirty Meter Telescope (TMT) was taken as a case to study. In order to develop lightweight structures which satisfies the design requirements for mass and stiffness, a design scheme of cylindrical composite shells supporting structure was proposed and their finite element models were developed. A size optimisation and a ply sequence optimisation of the composite structure were carried out. The structures before and after optimisation were evaluated from the aspects of mass, displacement, failure index and fundamental frequency. After the optimised design, the mass of the optimised WFOS cylindrical composite shell structure is reduced to approximately 50%, but its maximum displacement (0.513 mm) and fundamental frequency (8.275 Hz) are nearly unchanged. The study indicates that a cylindrical composite shell structure is an efficient structural form for large optical instruments.

scholarly journals Multicolor Survey For High Redshift Quasars By Kiso Schmidt Telescope

1998 ◽  
Vol 11 (1) ◽  
pp. 482-486
Author(s):  
Tomohiko Yamagata ◽  
Kimiaki Kawara ◽  
Tsutomu Aoki ◽  
Yoshiaki Sofue
Keyword(s):  
High Redshift ◽  
Wide Field ◽  
Schmidt Telescope ◽  
Field Surveys ◽  
Small Areas ◽  
Large Telescopes

Several groups have been successful in the survey of high-redshift (z > 4) quasars. For example, Schneider et al. (1994) and Schmidt et al. (1995) were successful in detecting 90 quasars with 2.75 < z < 4.75, R < 21 for 62deg2 using Palomar Transit Grism. Among them, there are 9 quasars with z > 4.0. Storrie-Lombardi et al. (1996) were detected 31 quasars with z > 4.0, mT < 19 for 2500deg2 by APM photographic multicolor survey using UK Schmidt telescope. Survey observations of quasars up to now have to select one of the following conditions; wide field surveys using photographic Schmidt plate which cover large areas but do not go faint enough, or deep surveys using large telescopes which go faint magnitude but which cover relatively small areas.

STM studies of crystal growth

1991 ◽  
Vol 49 ◽  
pp. 374-375
Author(s):  
M. G. Lagally
Keyword(s):  
Crystal Growth ◽  
Molecular Beam ◽  
Chemical Vapor ◽  
Sputter Deposition ◽  
Field Of View ◽  
Scanning Tunneling ◽  
Wide Field ◽  
Tunneling Microscopy ◽  
Wide Field Of View ◽  
The One

It has been recognized since the earliest days of crystal growth that kinetic processes of all Kinds control the nature of the growth. As the technology of crystal growth has become ever more refined, with the advent of such atomistic processes as molecular beam epitaxy, chemical vapor deposition, sputter deposition, and plasma enhanced techniques for the creation of “crystals” as little as one or a few atomic layers thick, multilayer structures, and novel materials combinations, the need to understand the mechanisms controlling the growth process is becoming more critical. Unfortunately, available techniques have not lent themselves well to obtaining a truly microscopic picture of such processes. Because of its atomic resolution on the one hand, and the achievable wide field of view on the other (of the order of micrometers) scanning tunneling microscopy (STM) gives us this opportunity. In this talk, we briefly review the types of growth kinetics measurements that can be made using STM. The use of STM for studies of kinetics is one of the more recent applications of what is itself still a very young field.

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