Multi-wavelength Optical Aperture Synthesis

1992 ◽  
Vol 10 (1) ◽  
pp. 71-73 ◽  
Author(s):  
R.G. Marson ◽  
T.R. Bedding ◽  
J.G. Robertson
Keyword(s):  
Radio Astronomy ◽  
Angular Resolution ◽  
Diffraction Limit ◽  
Double Star ◽  
Aperture Synthesis ◽  
Angular Diameter ◽  
Optical Aperture ◽  
Multi Wavelength ◽  
Red Giant ◽  
Large Telescopes

AbstractThe technique of aperture synthesis is well developed in radio astronomy. When applied to the optical regime, aperture synthesis allows one to partially overcome the blurring effects of the atmosphere and increase the angular resolution of large telescopes to the diffraction limit. MAPPIT (Masked APerture-Plane Interference Telescope) is a multi-element interferometer which operates at the coude focus of the 3.9 m Anglo-Australian Telescope. This instrument has recently been reconfigured to operate in a dispersed mode so that simultaneous observations in a band of wavelengths are possible. We will discuss this instrument’s new mode and present observations of the double star δ Sco and an angular diameter of the previously unresolved red giant β Gru.

Plans for the Australian Synthesis Telescope

1976 ◽  
Vol 3 (1) ◽  
pp. 7-11 ◽  
Author(s):  
K. J. Wellington
Keyword(s):  
Radio Astronomy ◽  
Angular Resolution ◽  
High Sensitivity ◽  
Aperture Synthesis ◽  
High Angular Resolution ◽  
The Past ◽  
New Synthesis

A major requirement of modern radio astronomy is the attainment of the highest possible angular resolution. This high angular resolution should be matched by a high sensitivity and by spectral and polarization capabilities. Study and experience have shown that no form of telescope is more effective in this respect than the aperture synthesis type. The past few years have seen a growing realization amongst astronomers, both here and overseas, of the need for a new synthesis telescope able to observe the full southern sky. This realization has been stimulated by several factors:

scholarly journals On the Importance of Active Image Stabilisation

1984 ◽  
Vol 79 ◽  
pp. 367-378
Author(s):  
J.E. Noordam
Keyword(s):  
Point Source ◽  
Speckle Interferometry ◽  
Aperture Synthesis ◽  
Atmospheric Conditions ◽  
Optical Telescope ◽  
Aperture Diameter ◽  
Logical Approach ◽  
Optical Aperture ◽  
Large Telescopes ◽  
Mirror Telescope

AbstractThe performance of an optical telescope can be improved considerably by opening the shutter only at moments of good seeing. The resulting instantaneous highresolution images must be corrected for shift before adding them all together. The optimum aperture diameter for which this technique works well is 1 meter or less, depending on atmospheric conditions. Image stabilisation not only improves the resolution and thus the point-source sensitivity, but it is also expected to improve the performance of speckle interferometry and optical aperture synthesis. This makes its implementation on large telescopes desirable. While it is certainly possible to do this by treating a large filled aperture like a set of independent subapertures, a much more logical approach would be to build an array of 1-meter telescopes, preferably mounted in a single large frame so that it can be pointed in all directions without extensive pathlength compensation. Such a “Many Mirror Telescope” has many advantages, and is feasible because image stabilisation helps to solve the beam-combining problem.

scholarly journals Imaging with a Coherence Interferometer in Optical Astronomy

1979 ◽  
Vol 49 ◽  
pp. 175-185
Author(s):  
C. Roddier ◽  
F. Roddier
Keyword(s):  
Atmospheric Turbulence ◽  
Angular Resolution ◽  
Weather Conditions ◽  
Diffraction Limit ◽  
Resolving Power ◽  
Large Telescopes ◽  
Optical Astronomy

In optical astronomy, images are highly degraded by atmospheric turbulence. The diameter of the seeing disk may vary from 0.2 arcseconds to 10 arcseconds or more according to weather conditions. A typical diameter is of the order of 2 arcseconds which is the angular resolution of a 6cm lens at the diffraction limit.Large telescopes have been built for their light collecting capabilities, not for their resolving power which is, in general, of the order of 0.2 arcseconds, that is far from the diffraction limit.

scholarly journals Upper Limits on Sub-Arcminute Fluctuations in the CBR

1992 ◽  
Vol 9 ◽  
pp. 333-334
Author(s):  
R. B. Partridge
Keyword(s):  
New Mexico ◽  
Radio Astronomy ◽  
Angular Resolution ◽  
Aperture Synthesis ◽  
Large Array ◽  
Astronomy Observatory ◽  
Very Large Array ◽  
Radio Astronomy Observatory ◽  
Upper Limits

The use of aperture synthesis allows one to search for fluctuations in the CBR on angular scales below 1 arcminute. I report here tentative results of an experiment carried out with E. B. Fomalont, R. Windhorst and J. Lowenthal using the Very Large Array of the National Radio Astronomy Observatory in New Mexico. We used the instrument in its tightest configuration and at a wavelength of 3.6 cm; the corresponding angular resolution was ~10”. We were able to set limits on fluctuations in the CBR on a range of angular scales, 10”-90”, and these are among the most sensitive upper limits on CBR fluctuations yet published.

High-resolution Imaging by Optical Aperture Synthesis: First Results from the MAPPIT Project

1991 ◽  
Vol 9 (1) ◽  
pp. 162-163 ◽  
Author(s):  
J. G. Robertson ◽  
T. R. Bedding ◽  
R. G. Marson ◽  
P. R. Gillingham ◽  
R. H. Frater ◽  
...  
Keyword(s):  
High Resolution ◽  
Double Star ◽  
Aperture Synthesis ◽  
High Time Resolution ◽  
High Resolution Imaging ◽  
Primary Mirror ◽  
Optical Aperture ◽  
First Results ◽  
Resolution Imaging ◽  
Fringe Patterns

AbstractWe have successfully demonstrated optical aperture synthesis at the 4-m Anglo-Australian Telescope. By using a multi-hole mask over the (re-imaged) primary mirror and recording the resulting fringe patterns with high time resolution, diffraction-limited images of sufficiently bright objects can be reconstructed. The data processing uses closure phases to overcome the effects of atmospheric turbulence. We show an image of the double star η Oph, with component separation 0″.45.

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.

Zooming into the complex dusty envelopes of C-rich AGB stars

2018 ◽  
Vol 14 (S343) ◽  
pp. 456-457
Author(s):  
Foteini Lykou ◽  
Josef Hron ◽  
Daniela Klotz
Keyword(s):  
Temperature Distribution ◽  
Near Infrared ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Dust Formation ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
Recent Advances ◽  
Multi Wavelength

AbstractRecent advances in high-angular resolution instruments (VLT and VLTI, ALMA) have enabled us to delve deep into the circumstellar envelopes of AGB stars from the optical to the sub-mm wavelengths, thus allowing us to study in detail the gas and dust formation zones (e.g., their geometry, chemistry and kinematics). This work focuses on four (4) C-rich AGB stars observed with a high-angular resolution technique in the near-infrared: a multi-wavelength tomographic study of the dusty layers of the circumstellar envelopes of these C-rich stars, i.e. the variations in the morphology and temperature distribution.

scholarly journals SUSI’s Potential for Double Star Research

1992 ◽  
Vol 135 ◽  
pp. 521-526
Author(s):  
John Davis
Keyword(s):  
Angular Resolution ◽  
Double Star ◽  
Double Stars ◽  
Stellar Interferometer ◽  
New Instrument

AbstractThe Sydney University Stellar Interferometer (SUSI) is currently undergoing commissioning and will soon commence its astronomical program in which observations of double stars will form a major component. With its 640-m long North–South array of input siderostats, the new instrument will have unprecedented angular resolution.

Sign in / Sign up

Export Citation Format

Share Document