Over the last two decades, an extensive body of knowledge has been developed concerning the effects of atmospheric turbulence on optical propagation. Much of this is directly relevant to astronomical imaging, and with proper interpretation, to the type of pseudo-imagery that is of concern to us at this conference. This paper will provide an overview of this matter, hopefully with sufficient insight developed that the reader will be able to quickly estimate the nature and magnitude of the turbulence effects to be expected in a pseudo-imagery process. The paper starts with a review of turbulence effects on conventional imagery, reviewing the “nondimensional” nature of the turbulence statistics, presenting the local measure of the optical strength of turbulence, , and developing the resolution scale, r0. It presents a statistical view of the nature of the wavefront distortion geometry, indicating the dominance of the random wavefront tilt component. The MTF for conventional imagery and for speckle interferometry (Labeyrie) is presented with comments concerning their relationship. Following that, the foundation of the speckle imagery concept (Knox-Thompson) is presented. Results are then set forth for the allowable spectral bandwidth in speckle techniques, as well as results defining the allowable field-of-view size (isoplanatism) and the allowable exposure time for speckle techniques. Taken all together, these results provide a basis for estimating most of the significant effects of atmospheric turbulence in speckle interferometry and speckle imagery.

This review of the lunar occultation technique summarizes results of 94 diameter measurements for 62 stars. The range of angular diameters measured, the coverage of spectral types, and the wavelengths studied are illustrated and discussedo Comparison with other techniques, magnitude limits and possible future developments are also considered.

Michelson,one-dimensional, and two-dimensional apertures are used to obtain the statistical properties of the solar granulation. The calibration of the power spectrum is performed via Michelson stellar interferometry as well as by the use of changes in seeing conditions during speckle-interferometric measurements. The correction of 40 analyses, determined with Fried's parameter ro ranging between 2.5 cm and 11.5 cm, provides satisfactory convergence for frequencies up to 3 cycles per arc second

The angular diameters ad shapes of bright infrared stars are now being measured from 2 micron to 20 microns using several newly developed techniques of high angular resolution interferometry. These objects possess circumstellar shells emitting in the temperature range 300-600K, thus the brightest of their number have sizes ranging from 0 1 to 10 arcseconds, and are readily resolved by instruments a few meters across.

The size, shape, and structure of several typesof stars will be discussed in detail as the Colloquium proceeds. It will be seen that this information can be used to help characterize the optical properties of the particulate material contained in the circumstellar envelopes. Conclusions concerning the formation and evolution of these cold outer regions of stars may also be possible It appears that the conditions in some of these circumstellar envelopes may be suitable for the formation of planets, a process which may be studied directly as these new techniques are further developed.

Although sensitivities of present instruments are still somewhat marginal, it is now possible to resolve the brightest of the extragalactic nuclei at 10 microns Future instrumental developments should bring the size and structure of many extragalactic nuclei within reach at several wavelengths, thus adding important information on the nature of these extraordinary sources of infrared emission