The 1990s are proving to be a very exciting p&iod for high angular resolution astronomy. At radio wavelengths a combination of new array instruments and pow­ erful imaging algorithms have generated images of unprecedented resolution and quality. In the optical and infrared, the great technical difficulties associated with constructing separated-aperture interferometers have been largely overcome, and many new instruments are now operating or are being developed. As these pro­ grams start to produce observational results they will be able to draw extensively on the experience gained by the radio-interferometry community. Thus it seemed that the time was ripe for a meeting which would bring together workers from all wavelength ranges to discuss the details of the science and art of "Very High Angular Resolution Imaging" . While the main emphasis of Symposium No. 158 was on high resolution tech­ niques from the radio, mm-wave, infrared and optical bands, it also provided an opportunity for presentation of astronomical results from these techniques. As well as giving our colleagues from the Northern Hemisphere a break from midwinter, the location of the Symposium in Australia recognised the continuing development of astronomical interferometry in this country, especially the recent completion of the Australia Telescope radio array, and the progress toward com­ missioning of the Sydney University Stellar Interferometer. A number of the par­ ticipants visited these instruments during the post-symposium tour.

Inhalt

Radio/Optical comparisons.- 1 Seeing [invited].- 2 Comparing optical and radio - quantum issues.- Transfer of Techniques.- 3 Heterodyne interferometry in the infrared [invited].- 4 The SAO submillimeter wavelength array.- 5 Imaging techniques: Limitations to the quality of images.- 6 Surprise and sociology in multi-disciplinary sciences.- Imaging Techniques.- 7 HST image restoration: current capabilities and future prospects [invited].- 8 Lunar occultations: from past to future achievements.- 9 Beam combination for wide field imaging.- 10 Direct maximum-entropy image reconstruction from the bispectrum.- 11 Source-noise in radio synthesis images of polarized sources.- 12 Phase calibration of the proposed millimeter array.- 13 VLBA phase-referencing.- 14 Radio arrays - mm to meters.- 15 The Very Long Baseline Array.- Radio Array Instruments.- 16 Recent results from the VLBA.- 17 MERLIN - A phase-stable `VLBI' array.- 18 The Southern Hemisphere VLBI Experiment program, SHEVE.- Optical and Infrared Interferometers and Arrays.- 19 The Sydney University Stellar Interferometer (SUSI).- 20 The VLT Interferometer.- 21 The Big Optical Array.- 22 Progress on GI2T.- 23 The COAST interferometer.- 24 An adaptive steerable imaging array.- 25 CIROI project.- Instrumentation and Techniques.- 26 The baseline metrology system of the USNO astrometric interferometer.- 27 Design and construction of a beam combiner and related hardware.- 28 An overview of the SUSI control system.- 29 The fringe tracking servo in SUSI.- 30 Motion of the delay lines of an optical interferometer when reconstructing an image by redundant spacing calibration.- 31 The micro-precision interferometer testbed instrument design.- 32 Phase and image reconstruction from pupil-plane observations in the near infrared: integration of the phasors.- 33 Radio source variability as a tool for very high resolution.- Imaging Theory.- 34 Iterative blind deconvolution method with use of Lucy's algorithm: application to IR speckle data.- 35 Speckle imaging with the bispectrum and without reference star.- 36 CLEAN/MEM deconvolution errors: semicompact sources.- 37 Generalized versus classical maximum entropy for imaging.- 38 Super-resolution by phase-gradient unravelling.- 39 Restoration over fields of view wider than the isoplanatic patch.- 40 Differential diffraction in Michelson stellar interferometry.- Impact of Technology I: Radio and Millimeter Waves.- 41 Optical fibres in radioastronomy.- 42 Recent developments in mm and sub-mm interferometry.- 43 High resolution radio source maps at 73.8 MHz.- 44 AIPS++: A new astronomical imaging package [invited] 2.- Impact of Technology II: Optical and Infrared.- 45 Latest technical developments at the infrared spatial interferometer.- 46 Integrated optics in astronomical interferometry.- Adaptive Optics and Seeing.- 47 Adaptive optics: performance and limitations.- 48 Laser guide star adaptive optics: present and future.- 49 Laser guide star adaptive optics on the 1.5 m telescope at the Starfire Optical Range.- 50 Minimum redundant aperture masking interferometry with tip-tilt wavefront correction.- 51 Observations of seeing at 0.5 and 12.4µm.- 52 Preliminary seeing measurements for SUSI.- 53 Aspects of the theoretical performance of modal adaptive optics.- 54 Simulation study of a low-light-level wavefront sensor driving a low-order, near-IR adaptive optics system.- Aperture Distributions.- 55 Fringe visibility and phase measurements [invited].- 56 Speckle vs non-redundant masking [invited].- 57 MAPPIT: optical interferometry with non-redundant masks.- 58 Optimal linear arrays for wide bandwidths.- 59 High resolution and high sensitivity spectral-line imaging with multiple arrays.- Imaging Results: Radio and Millimeter Waves.- 60 High resolution imaging forty years ago.- 61 Results with the extended MERLIN.- 62 High resolution image reconstruction at Yunnan Observatory.- 63 High resolution imaging at mm-wavelengths with the Hat Creek Array.- 64 Miyun 232 MHz survey and some new imaging techniques.- 65 Compact array mapping of the nuclear starburst in NGC 7552.- 66 ATCA radio polarization observations of NGC 1566 and NGC 1672.- 67 Fluctuations of polarized radiation in a random magnetoplasma.- 68 High angular resolution observations of Her 36.- 69 The Caltech-Jodrell Bank (CJ) VLBI snapshot surveys.- Imaging Results: Optical and Infrared.- 70 First experimental results from pupil masking on a solar telescope.- 71 Optical interferometry in the multi-speckle mode.- 72 Near infrared high angular resolution observations of stars and circumstellar regions by the technique of lunar occultations.- 73 Diffraction-limited near infrared imaging of the central parsec of the Galaxy.- 74 Long baseline interferometric observations of 3 circumstellar dust shells at 11 microns.- 75 High angular resolution observations of protostellar disks.- 76 The extended Ha component of T Tau.- 77 An interferometric survey of Mira variables and M supergiants.- 78 Speckle observations of solar granulation.- 79 Comparison of HST and VLA images at 0.1" of the Orion nebula.- 80 An HR diagram for the LMC from the medium deep survey.- 81 Stellar diameters, limb darkening, extended atmospheres and shells: observations with the Mark III Inteferometer.- 82 Mark III Interferometer: milliarcsec "visual" orbits of spectroscopic binaries.- 83 High resolution interferometric observations of eclipsing binary stars.- 84 Lunar occultations of young stellar objects in the Taurus and Ophiuchus star forming regions.- 85 Pupil plane interferometry: some conclusions from SCASIS.- 86 RIRAS: high-resolution IRAS images.- Astrometry.- The present status of astrometry at optical and radio wavelengths [invited, presented by G Westerhont] 423.- 87 The USNO Astrometric Interferometer [invited].- 88 VLBI astrometry [invited].- 89 High precision differential astrometry in large angular separation pairs of radiosources.- 90 Five years of stellar position measurements with the Mark III optical interferometer.- Frontier Techniques.- 91 Imaging with a gravitational lens [invited].- 92 Radar imaging of the planets using the Very Large Array.- Future Prospects.- 93 Limitations to optical/IR interferometry from the ground and space.- 94 The ultimate radio resolution [invited].- 95 Progress of the Optical Very Large Array [invited presented by I Tallon-Bosc].- 96 The cosmological application of very high angular r…