Techniques for High Angular Resolution Astronomical Imaging

1997 ◽  
pp. 1-34
Author(s):  
J. M. Beckers
Keyword(s):  
Angular Resolution ◽  
High Angular Resolution ◽  
Astronomical Imaging

scholarly journals Thin Shell, Segmented X-Ray Mirrors

2010 ◽  
Vol 2010 ◽  
pp. 1-16 ◽  
Author(s):  
R. Petre
Keyword(s):  
Angular Resolution ◽  
Imaging System ◽  
Broad Band ◽  
Thin Foil ◽  
Substantial Improvement ◽  
High Angular Resolution ◽  
X Ray ◽  
Performance Improvements ◽  
Glass Substrates ◽  
Astronomical Imaging

Thin foil mirrors were introduced as a means of achieving high throughput in an X-ray astronomical imaging system in applications for which high angular resolution was not necessary. Since their introduction, their high filling factor, modest mass, relative ease of construction, and modest cost have led to their use in numerous X-ray observatories, including the Broad Band X-ray Telescope, ASCA, and Suzaku. The introduction of key innovations, including epoxy replicated surfaces, multilayer coatings, and glass mirror substrates, has led to performance improvements and in their becoming widely used for X-ray astronomical imaging at energies above 10 keV. The use of glass substrates has also led to substantial improvement in angular resolution and thus their incorporation into the NASA concept for the International X-ray Observatory with a planned 3 m diameter aperture. This paper traces the development of foil mirrors from their inception in the 1970s through their current and anticipated future applications.

scholarly journals Principles of Imaging Using Arrays

1989 ◽  
Vol 8 ◽  
pp. 547-548
Author(s):  
T.J. Cornwell
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Angular Resolution ◽  
Radar Imaging ◽  
High Angular Resolution ◽  
Radio Interferometry ◽  
Resonance Imaging ◽  
The Past ◽  
Astronomical Imaging ◽  
Single Aperture

Since diffraction-limited imaging with a single aperture yields angular resolution ~ λ/D, the attainment of high angular resolution with single apertures requires the construction of correspondingly large monolithic apertures, the whole surface of which must be figured to much less than a wavelength. At the longer wavelengths, it is impossible to build a sufficiently large single aperture: for example, at λ21 cm, arcsecond resolution requires an aperture of diameter ~ 50 km. At the shorter wavelengths, the atmosphere imposes a natural limit in resolution of about one arcsecond. However, another route is possible: that of using synthetic apertures to image the sky. The problem of figuring synthetic apertures is considerably simpler, and can be implemented in a computer. Synthetic apertures are now in use in many fields, e.g. radio-interferometry, radar imaging, magnetic resonance imaging. Radio-interferometric techniques developed in radio-astronomy over the past forty years are now being applied to optical and IR astronomical imaging by a number of groups.

Small-Angle Electron Scattering (SAES) of Polymers

1985 ◽  
Vol 43 ◽  
pp. 78-79
Author(s):  
Ralph Oralor ◽  
Pamela Lloyd ◽  
Satish Kumar ◽  
W. W. Adams
Keyword(s):  
Electron Scattering ◽  
Small Angle ◽  
Angular Resolution ◽  
Structural Features ◽  
Objective Lens ◽  
High Angular Resolution ◽  
Push Button ◽  
First Case ◽  
Diffraction Mode ◽  
Very High

Small angle electron scattering (SAES) has been used to study structural features of up to several thousand angstroms in polymers, as well as in metals. SAES may be done either in (a) long camera mode by switching off the objective lens current or in (b) selected area diffraction mode. In the first case very high camera lengths (up to 7Ø meters on JEOL 1Ø ØCX) and high angular resolution can be obtained, while in the second case smaller camera lengths (approximately up to 3.6 meters on JEOL 1Ø ØCX) and lower angular resolution is obtainable. We conducted our SAES studies on JEOL 1ØØCX which can be switched to either mode with a push button as a standard feature.

Large-angle convergent-beam electron-diffraction study of coherent precipitates and decorated dislocations

1996 ◽  
Vol 54 ◽  
pp. 1002-1004
Author(s):  
J.M.K. Wiezorek ◽  
H.L. Fraser
Keyword(s):  
Electron Diffraction ◽  
Angular Resolution ◽  
Large Angle ◽  
Electron Diffraction Study ◽  
Convergent Beam Electron Diffraction ◽  
Crystal Defects ◽  
High Angular Resolution ◽  
Beam Electron ◽  
Diffraction Plane ◽  
Convergent Beam

Conventional methods of convergent beam electron diffraction (CBED) use a fully converged probe focused on the specimen in the object plane resulting in the formation of a CBED pattern in the diffraction plane. Large angle CBED (LACBED) uses a converged but defocused probe resulting in the formation of ‘shadow images’ of the illuminated sample area in the diffraction plane. Hence, low-spatial resolution image information and high-angular resolution diffraction information are superimposed in LACBED patterns which enables the simultaneous observation of crystal defects and their effect on the diffraction pattern. In recent years LACBED has been used successfully for the investigation of a variety of crystal defects, such as stacking faults, interfaces and dislocations. In this paper the contrast from coherent precipitates and decorated dislocations in LACBED patterns has been investigated. Computer simulated LACBED contrast from decorated dislocations and coherent precipitates is compared with experimental observations.

Binary Cepheids From High-Angular Resolution

2015 ◽  
Vol 71-72 ◽  
pp. 187-188
Author(s):  
A. Gallenne ◽  
A. Mérand ◽  
P. Kervella
Keyword(s):  
Angular Resolution ◽  
High Angular Resolution

350 Micron Continuum Imaging of the Orion A Molecular Cloud with the Submillimeter High Angular Resolution Camera

1998 ◽  
Vol 509 (1) ◽  
pp. 299-308 ◽  
Author(s):  
D. C. Lis ◽  
E. Serabyn ◽  
Jocelyn Keene ◽  
C. D. Dowell ◽  
D. J. Benford ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Angular Resolution ◽  
High Angular Resolution

scholarly journals Hunting for intermediate-mass black holes in globular clusters: an astrometric study of NGC 6441

2021 ◽  
Vol 503 (1) ◽  
pp. 1490-1506
Author(s):  
Maximilian Häberle ◽  
Mattia Libralato ◽  
Andrea Bellini ◽  
Laura L Watkins ◽  
Jörg-Uwe Pott ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Velocity Dispersion ◽  
Angular Resolution ◽  
Hubble Space Telescope ◽  
High Mass ◽  
High Angular Resolution ◽  
Stellar Kinematics ◽  
Intermediate Mass ◽  
The Core ◽  
Large Telescopes

ABSTRACT We present an astrometric study of the proper motions (PMs) in the core of the globular cluster NGC 6441. The core of this cluster has a high density and observations with current instrumentation are very challenging. We combine ground-based, high-angular-resolution NACO@VLT images with Hubble Space Telescope ACS/HRC data and measure PMs with a temporal baseline of 15 yr for about 1400 stars in the centremost 15 arcsec of the cluster. We reach a PM precision of ∼30 µas yr−1 for bright, well-measured stars. Our results for the velocity dispersion are in good agreement with other studies and extend already existing analyses of the stellar kinematics of NGC 6441 to its centremost region never probed before. In the innermost arcsecond of the cluster, we measure a velocity dispersion of (19.1 ± 2.0) km s−1 for evolved stars. Because of its high mass, NGC 6441 is a promising candidate for harbouring an intermediate-mass black hole (IMBH). We combine our measurements with additional data from the literature and compute dynamical models of the cluster. We find an upper limit of $M_{\rm IMBH} \lt 1.32 \times 10^4\, \textrm{M}_\odot$ but we can neither confirm nor rule out its presence. We also refine the dynamical distance of the cluster to $12.74^{+0.16}_{-0.15}$ kpc. Although the hunt for an IMBH in NGC 6441 is not yet concluded, our results show how future observations with extremely large telescopes will benefit from the long temporal baseline offered by existing high-angular-resolution data.

Sign in / Sign up

Export Citation Format

Share Document