A review of the applications of a point-symmetric, 180-degree, rotational shearing interferometer is given. Material includes, photographs of the Michelson stellar interferometer fringes from α Lyr, measures of amplitude of phase excursions in the atmosphere, and a measure of the order of interference in speckle patterns. New material includes unpublished double star speckle patterns to illustrate the isoplanatic patch, a measure of the time fluctuations of the earths' atmosphere, and measurements of the properties of a 256 channel linear reticon.

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.

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

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