A number of ultraviolet-excess galaxies have been detected during the course of our surveys using the Kiso Schmidt telescope. In this report, a classification scheme is proposed for 142 selected objects on the basis of their morphological features, and the relation between the morphological type and the degree of ultraviolet-excess is presented. In general irregular galaxies with conspicuous H II regions and pair galaxies tend to show higher degree of ultraviolet-excess, while the degree in spiral galaxies appears to range widely.

The role of the Schmidt telescopes in the discovery of the Quasi Stellar Objects and of the Active Galactic Nuclei, and in the understanding of their properties was and continues to be of the greatest importance. Thousands of Radio-Sources have been quickly associated to their optical counterparts thanks to the worldwide availability of the Palomar Observatory Sky Survey plates and charts and more recently of the films of the ESO B Survey. Other thousands of QSOs and AGNs devoid of radio emission are found by the large Schmidts nowaday in operation. This wealth of data give fundamental cosmological knowledge and insight in the physical processes occuring in these objects. I'll concentrate in this Review on two specific topics, namely on the discovery techniques and on the study of the optical variability. To both subjects, the 67/92 cm Schmidt telescope here at Asiago has made significant contributions. The first topic is treated in several excellent papers, such as the one by M. Smith (1978) and the one by P. Veron (1983); the material presented in the second part is largely new. In the following, I'll use rather loosely the terms QSOs and AGNs to designate a variety of objects including Quasars (those QSOs in catalogs of Radio-Sources), high-redshift compact galaxies with emission lines, BL LACset similia.

We have presented here some results of our search for quasars near large galaxies. Papers on these results are to be published shortly in Monthly Notices of the Royal Astronomical Society (Mon. Not. R. astr. Soc.)

The aim of our programme is to use the absorption spectra of QSOs and related objects (BL Lacs, Seyfert galaxies) as probes of the interstellar media of intervening galaxies. For such a study it is necessary to find new suitably bright QSOs and related objects lying close on the sky to large galaxies because very few are known at present.

In recent years the development of fast optical telescopes with large corrected fields, of fine-grained, high DQE emulsions such as IIIa-J/F, and the use of rapid scanning microdensitometers and computers, have all made deep photometric studies of large areas of the sky tractable. I am in the process of conducting such a survey using the prime focus cameras of the CTIO and KPNO 4-meter telescopes. Skylimited plates are taken in four colors defined by filter/emulsion characteristics. Pertinent information about the photometric system is given in Table 1. The large database from this survey of about fifteen areas of the sky is being used to address many problems both extragalactic and galactic in nature. A preliminary report on studies of faint blue stellar objects, quasar candidates, will be presented here for seven of the fifteen fields. Table II lists some information about the fields used for this study.

Recent measurement of UK Schmidt plates have yielded interesting results on the cross-correlation of galaxies with QSOs and ultra-violet excess (UVX) objects. We find that in all Schmidt fields so far analysed there appears to be a significant anti-correlation (at angular scales less than 5') between the positions of galaxies and QSOs and between the positions of galaxies and UVX objects. This anti-correlation appears to be restricted to those galaxies that are found in clusters. These observations can very naturally be explained using a model in which dust within clusters of galaxies obscures the QSOs lying at cosmological distances behind them. This hypothesis may be further corroborated by tentative evidence that the UVX objects and the QSOs appear to be reddened close to clusters of galaxies.

3C 446 is one of the most violently variable quasars.

Its optical variability has been studied for instance by Barbieri et al. (1978), by Pollock et al. (1979) and by Miller (1981). The quasar exibits periods of prolonged activity, with amplitude exceeding 3 mag, and with intraday significant variations. We observed 3C kkG in the last month of Aug. 1983, finding the quasar of unpreceeded brightness.

Three plates were obtained with the 67/92 cm Schmidt telescope on Aug. k, 9 and 11, and in all three the quasar is seen at B=15.1, the brightest value ever recorded. We have only one previous plate of low quality taken on July 31, and 3C kkG is fainter by approximately 0.7 mag. Finally, on two plates taken the 27th of Aug. with the 182 cm telescope at Cima Ekar we see it again down to B=16.2.

This is the second Asiago blue objects field studied to determine the physical nature of ultraviolet excess objects (UVX) at high galactic latitudes using low dispersion objective prism plates. As the first of this series ( Abati 1982 )this work has a double aim:

1. 1. to determine the proportions in the component populations of UVX objects selected by the two-colour method on Schmidt telescope plates;

2. 2. to determine the surface density of quasars down to a limiting magnitude m = 18 mag.

Three radio identification programmes are described which are drawn from radio samples with accurate radio positions (< 2" arc rms). Optical identifications are being made on the basis of radio-optical positional coincidence alone, without regard to colour or morphology, using the UKST IIIa-J sky survey to a limiting magnitude of 22.5. Some preliminary results are presented.

Counts of faint galaxies should reveal any evidence of galaxy luminosity or color evolution, as well as new information on the faint end of the galaxy luminosity function. The FOCAS automated detection and classification software is reviewed, and results of the deep 4m PF photographic survey to 24th magnitude in 23 fields covering 9 sq. degrees are presented. Color-magnitude plots for stars and galaxies are shown, and galaxy color evolution is discussed. Evidence is found for a faint galaxy blue trend at 22-24 J mag. However, the k-correction becomes so severe at redshift ~1 that the intrinsically fainter galaxies are emphasized in any magnitude-limited survey. No unambiguous evidence is found for evolution. New 4m limit CCD multi-color data are shown and discussed. The limiting magnitude for detection is 27th J magnitude in 2 hours integration. The data exclude evolution starting at any one epoch for z<10.

Using photographic data obtained from the U.K. Schmidt and Anglo-Australian telescopes we have determined galaxy number counts in the range 17m≤B≤23m and 15mm≤R≤22m. By comparing our observations with models we find that the blue counts show strong evidence for galaxy luminosity evolution. We find that the red counts are better fitted by non-evolving models and that, here, the effects of the cosmological deceleration parameter, qo, and luminosity evolution are comparable. We discuss the implications of these results, with particular reference to the prospects of using the red counts to obtain constraints on qo.

About 25 years ago Zwicky (1957), Holmberg (1958) and Hoffmeister (1962) found intergalactic dust by observations. Zwicky (1957) explained the deficiency of distant clusters of galaxies by intergalactic dust inside the near clusters. Holmberg (1958) made extensive observations of the Virgo cluster. He found systematic differences of the colour indexes between cluster and field galaxies. Intergalactic dust inside of the Virgo cluster should be the reason of these differences. Hoffmeister (1962) found a clear deficiency of galaxies in the region of Microscopicum. Again the reason should be a large cloud of intergalactic dust.

The history of the Universe is infinitely more interesting than the history of the study of the Universe.

PROLOGUE

The understanding we have today of the distribution of galaxies resolves some of the debates which were going on in the seventies. Future data and analysis may allow us to discriminate among cosmological models.

Galaxy spectral evolutionary models are used to compute the following quantities in optical and UV bandpasses: (a) galaxy color, luminosity, two-color diagrams, and surface brightness profiles as functions of redshifty and (b) galaxy counts, and color and redshift distributions as functions of apparent magnitude. These predictions may be used as a guide to prepare and interpret observing runs with the Space Telescope, the Space Schmidt Telescope, and the Starlab Observatory.

The basic principle of the camera described by Bernard Schmidt in 1932 is that a single concave mirror with a stop at its center of curvature has no unique axis and therefore yields equally good images at all points of its yield. The field is curved, and to correct the spherical aberration produced by the mirror, Schmidt introduced, in the stop at the center of curvature of the mirror, a thin non spherical corrector plate of glass. Around 1930 at the Hamburg Observatory and in spite of many difficulties, it was Schmidt's genius as an optician that succeeded - after several judiciously interpreted trials - in figuring a corrector plate by elastic relaxation, and thus demonstrated the optical performance of this new generation of instruments.

The full potential of the next generation of larger telescopes will be realized only if they have well instrumented large fields of view. Scientific problems for which very large ground-based optical telescopes will be of most value often will need surveys to very deep limits with imaging and slitless spectroscopy, followed by spectroscopy of faint objects taken many at once over the field. Improved instruments and detectors for this purpose are being developed. Remotely positioned fibers allow the coupling of light from many objects in the field to the spectrograph slit. CCD arrays, operated in the TDI or drift scan mode, will make large area detectors of high efficiency that may supercede photographic plates. An ideal telescope optical design should be based on a fast parabolic primary, have a field of at least 1° with achromatic images < 0.25 arcseconds and have provision for dispersive elements to be used for slitless spectroscopy and compensation of atmospheric dispersion over the full field. A good solution for a general purpose telescope that can satisfy these needs is given by a three element refractive corrector at a fast Cassegrain focus. A specialized telescope dedicated to sky surveys, with better image quality and higher throughput than presently available, might be built as a scaled up Schmidt with very large photographic plates. Better performance in most areas should be obtained with a large CCD mosaic detector operated in the drift scan mode at a telescope with a 2-mirror reflecting corrector.

The Space Telescope is described from the viewpoint of its interaction with Schmidt telescopes, specifically with regard to the planning and interpretation of observations and to the construction of the Guide Star Selection System.

The reduction of Schmidt plates is divided into scanning the plates, processing the data, and analyzing the results. At least two new measuring machines for analyzing Schmidt plates are being designed which will increase the total throughput to over 10 plates per day. The developments of microprocessors and mass storage open new possibilities for faster and cheaper processing of these large amount of data. Finally, the introduction of DataBase Management and Table Data systems will make it easier for astronomers to analyze the extracted informations. With these new developments the aim to make a detailed analysis the plates at the same rate at which they are obtained can be achieved within this decade.