The IAU Colloquium No.49, on the formation of images from spatial coherence functions in astronomy, was held at Groningen, the Netherlands, during the period 10-12 August 1978. The colloquium was attended by 108 participants from 14 countries (U.S.A. 29, the Netherlands 20, U.K. 19, Germany 10, France 7, Australia 5, Canada 5, Japan 4, India 2, New Zea­ land 2, Sweden 2, Argentina I, Belgium I, Israel I). It was sponsored by the Netherlands Foundation for Radio Astronomy, the International Astronomical Union, the Department of Education and Sciences, the Union Radio-Scientifique Internationale, the Leiden Kerkhoven-Bosscha Foundat­ ion and the State University at Groningen. This volume contains 36 of the 37 papers presented. Nearly all papers are followed by a sununary of the discussion that took place after their presentation. A few papers, published in full elsewhere, are given only as abstracts. The majority of the papers are related to aperture synthesis in radio astronomy; a small number deal with optical astronomy and with applications in acoustics and medicine. The presentations are divided in 7 groups: aperture synthesis and its deficiencies, the problem of limited or missing phase information, techniques for processing and data display, optical interferometric methods, maximum entropy image reconstruction, other image improvement methods, and a survey of image formation from projections. Each group contains one or two invited lectures (see Table of Contents), intended as surveys of particular areas; on the average they occupy twice as many pages as the other papers.

Inhalt

I - Aperture Synthesis Methods.- Fundamentals and Deficiencies of Aperture Synthesis (Invited paper).- The Two Dimensional Representation of Three Dimensional Interferometer Measurements.- Measurement Errors in Rotational Synthesis and their Effects in the Map Plane (Invited Paper).- "Kneading": The Adjustment of Instrumental Phase and Gain Parameters to Suppress Error Patterns in a Synthesis Map.- A proposal to Obtain Short Spacing Information by Interpolation.- The Short Spacings Problem in Correlation Interferometers and a Procedure for Solving It (Abstract).- Short Spacing Synthesis from a Primary Beam Scanned Interferometer.- II - Aperture Synthesis With Limited Or No Phase Information.- Fundamental Aspects of Aperture Synthesis with Limited or No Phase Information (Invited paper).- Map-making with Non-phase Stable Interferometers.- Image Reconstruction from VLBI Amplitude and Phase Closure Data (Abstract).- On the Danger of Applying Statistical Reconstruction Methods in the Case of Missing Phase Information.- Reduction of Phase Noise in Interferometry with State-space Analysis.- III - Processing Techniques And Display Methods.- Digital Processing Methods for Aperture Synthesis Observations (Invited paper).- Digital Hardware Processing of Rotational Synthesis Data (Abstract).- Analogue Processing Methods for Synthesis Observations (Invited paper).- Exploring Methods of Effective Data Display in an Interactive Astronomical Data-processing Environment (Invited paper).- Processing and Display of Spectral Line Absorption Maps (Abstract).- A Proposed Correlator Back-end for the Culgoora Radio-heliograph.- An Acousto-optical Image Processor and Its Application to a 160 MHz Interferometer.- IV - Optical Interferometric Methods.- Imaging with a Coherence Interferometer in Optical Astronomy.- Towards Imaging of Star Clusters by Speckle Interferometry.- V - Maximum Entropy Image Reconstruction.- Resolution Enhancement: the 'Maximum Entropy Method' and the 'High Resolution Method' (Invited paper).- The Maximum Entropy Method (Invited paper).- The Use of Bayesian Statistics in Image Estimation from Interferometer Data.- Problems with Maximum Entropy (Abstract).- The Introduction of A Priori Knowledge in Certain Processing Algorithms.- Extending the Fourier Transform - The Positivity Constraint.- The Information of Images and Its Dependence on Noise and Spatial Resolution.- Maximum Entropy Spectral Analysis - Some Comments (Abstract).- VI - Other Image Improvement Methods.- The Method CLEAN - Use, Misuse and Variations (Invited paper).- Fitting a Gaussian Model to Aperture Synthesis Data by Akaike's Information Criterion (AIC).- An Optimum Deconvolution Method.- Application of the Simplex Algorithm to Image Restoration (Abstract).- Observations of Extended Radio Sources Using a Multiple-beam Technique.- Formation of Acoustic Images from Spatial Coherence Functions: Processing by Superresolution Techniques.- VII - Relevant Inputs from other Fields.- Reconstruction from Projections in Medicine and Astronomy (Invited paper).- Name index.