We describe a program of determining proper motions from digitized scans of Palomar Oschin Schmidt telescope plates at the Space Telescope Science Institute. Our method is most useful over 11 ≲ V ≲ 18 and .

As a first step of our open cluster programme a catalogue of proper motions and photographic U, B, V, R magnitudes for stars up to 18 mag within a region centered near Alcyone is presented. The catalogue is based on MAMA measurements of plates taken with Tautenburg and OCA (CERGA) Schmidt telescopes. The photometric survey includes ca. 65000 stars and covers a total field of about 25 square degrees. Proper motions have been obtained for ca. 40000 stars within a central 17 square degree region of this field. For the majority of stars in the survey an accuracy of 0.08 mag and 2 mas/year has been estimated for photometric data and proper motions, respectively. The results of the determination of the Pleiades membership up to 18th magnitude is presented.

In order to establish the probability of physical membership of open clusters by means of astrometrical methods, two criteria are used: the position distribution of stars in the sky and their proper motions. Proper motion methods have shown validity from a practical point of view; but are difficult to apply where there is a high ratio of cluster-to-field stars, and in crowded fields of the Milky Way.

As a test we have selected the nearby (170–190 pc) Blanco Cluster 1 (1 = 16°, b = −73°) in order to avoid complications arising from crowded fields. Photometric data however, suggests that the diameter of the cluster is rather extended (~ 120 arcsec). This will require a large-field solution, rather than a small-field solution which can be obtained with greater accuracy using Schmidt astrometry (Fresneau 1978; Nakamura & Sekiguchi 1993).

The use of proper motions and parallaxes for large numbers of stars, obtainable from a combination of Schmidt telescopes and automatic plate scanners, is discussed. The importance of deriving the zero points of both absolute proper motion, and of parallactic motion, is emphasised. Calibrations of proper motion and of parallaxes should be based on dispersions of proper motion. These methods are illustrated by results from a study in the South Galactic Cap.

Astrometric investigations undertaken with the 70 cm meniscus and 40 cm double astrograph telescopes are considered. We describe the determination of accurate positions for minor planets, giant-planet satellites, late-type stars, extragalactic radio-sources, optically discovered quasars and compact extragalactic objects in the Second Byurakan Survey.

The early optical identifications of radio sources were restricted to bright galaxies and to quasars with ultraviolet excesses, since such objects were rare and unlikely to land by chance within the large radio position error boxes. Other types of objects, such as very high redshift quasars and distant galaxies, were discriminated against because they did not look unusual and so were not readily recognised. Eventually much more accurate interferometric radio positions became available, enabling unambiguous identification of many optically faint objects. Now the internal accuracy of the radio positions can exceed that of the optical positions, requiring optical astrometry to be done to higher precision than ever before. A related problem is the correct registration of the two reference frames, which should be solved soon using a combination of data from the Hipparcos satellite and the Hubble Space Telescope.

The digitised data now available from the Schmidt sky surveys make it possible to automate the optical identification of sources, such as those in the IRAS infrared and Rosat X-ray surveys. Very accurate digitised optical surveys are also needed to prepare lists of targets for multi-object spectroscopy using fibre optic systems.

Modern models of Galaxy formation make fairly specific predictions which are amenable to detailed tests with galactic kinematic and chemical abundance data. For example, popular Cold Dark Matter models ‘predict’ growth of the Galaxy about a central core, which should contain the oldest stars. Later accretion of material forms the outer halo and the disks, while continuing accretion will continue to affect the kinematic structure of both the outer halo and the thin disk. This picture, which contains aspects of both the monolithic (‘ELS’) and the multifragment (‘Searle-Zinn’) pictures often discussed in chemical evolution models, makes some specific predictions which can be tested. The essential feature of these predictions is that they are believable only for the largest scale effects. Large scale properties of the Galaxy must be measured to test them. It is these studies which need large angular scale data. One specific example of current interest is the ‘prediction’ that mergers of small satellites are an essential feature of galactic evolution. This leads one to look for kinematic and spatial structures, and ‘moving groups’, as a primary test of such models.

The combination of Tautenburg plates and automatic measuring machines provides a powerful tool to obtain photometry and proper motions of a great number of stars for statistical investigations of our Galaxy. Photographic photometry with an accuracy of about 0.07 mag can be obtained provided two plates of the same colour and a sufficient number of photometric standards are available. With two plate pairs and a 20 years baseline, a proper motion accuracy better than 4 mas/year can be achieved for stars over a wide range of magnitudes. Outside the Galactic plane proper motions are determined with respect to hundreds of background galaxies.

We present a case study on the stellar space distribution of stars with MK spectral types B8 to A2 (dA) and gG8 to gK2 (gK) in a sky region of 25 square degrees, centred at the galactic coordinate l = 4° and b = +12°. Two hundred and forty-eight (248) stars with MK type of B8–A2 and gG8–gK2 were identified in this field. The space density distributions of these stars were obtained by employing the Matrix and Malmquist methods. The relative density of B8–A2 stars tends to be similar to that of gG8–gK2 stars, which implies that the two groups of stars occupy the same space volume in the galaxy. The comparison with those of Field-3 (l = 0.8°, b = –10°) show that the space density distribution of the two groups of stars above and below the galactic plane is not the same. Above the galactic plane, the space density of the gK stars is higher than those of dA stars, whereas below the galactic plane the density of dA stars is higher than for the gK stars. For both groups, the maximum space density occurs at around 30–40 pc from the galactic plane.

A determination of the C/M5+ ratio, as a function of the galactocentric distance, in the galactic disk is presented. These results are based upon previous determinations of the space density for cool carbon stars and for late giant M stars in the Milky Way. Most of these results were obtained from objective-prism surveys in the near infrared using mainly Schmidt-type telescopes. The ratio C/M5+ appears to increase from 0.05 to 0.25 in the galactic disk, from the galactic center outwards. A mean value of 0.15 of this ratio for the Galaxy is suggested. Correlations between the C/M5+ ratio and currently known metal abundance gradients in the galactic disk are discussed.

The Edinburgh-Cape Blue Object Survey is a major survey to discover blue stellar objects brighter than B ∼ 18 in the southern sky. It covers an area of sky of 10,000 square degrees with |b| > 30° and δ < 0°. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy are being obtained with the SAAO telescopes to classify objects brighter than B = 16.5. This paper describes the survey, the techniques used to extract the blue stellar objects, the photometric accuracy, and the completeness of the survey.

The Henry Draper stars are being systematically classified on the MK System, using the Curtis and Burrell Schmidt telescopes with photographic spectra having a dispersion of 108 Å/mm. Over 156,000 stars south of δ = +5°, have been classified leaving about 69,000 yet to do. The project is expected to be completed around the year 2004. This all-sky network of consistently classified spectra of very good quality should serve as a basis for future deep surveys. Such surveys will almost certainly be automated because of the huge number of stars to be dealt with. Von Hippel et al. at Cambridge plan to scan at least 150,000 of the spectra classified by Houk, using her plates to serve as a ‘training’ set for automatic classification using artificial neural networks. The same data can also be utilized for other methods of automatic classification including the metric-distance methods used by Kurtz and La Sala (Kurtz 1983). Even at lower dispersions, significantly more information can be obtained from Schmidt spectra than by doing Schmidt photometric colour surveys alone, though these are also valuable, especially when used in conjunction with spectra. We urge that large Schmidts not currently having prisms or other dispersive elements consider adding this equipment.

We are conducting a survey of the southern sky to study the properties of the lowest mass stars and the sub-stellar brown dwarf population thought to exist at masses below 0.08 M⊙. The survey makes use of plates from the UK and ESO Schmidt telescopes, using the new SuperCOSMOS plate measuring machine at Edinburgh to provide a catalogue of photographic BRI colours and proper motion measurements. Candidates are selected by extreme R–I colour (> 2.5) to a plate-limited magnitude of I ≈ 19.0 and R ≈ 21.0. The size of the survey is only limited by the progress of the UK Schmidt I band survey and the availability of photometric data for calibration of SuperCOSMOS measurements. It is anticipated that the survey will form part of a multi-colour proper motion database of southern sky objects.

Optical late M stars (spectral type later than M4) with IRAS colours of 0.7 < m12 − m25 < 1.6 belong to two possible luminosity classes; giants or supergiants (Raharto 1994). We have searched for supergiant candidates among the late M stars at low galactic latitude, between galactic longitude 351° < l < 1° and galactic latitude −2° < b < +2°, using data from the M star Catalogue (Raharto et al. 1984) and the IRAS Point Source Catalogue (Beichman et al. 1987). The search area is located in the direction of the galactic centre. M supergiants found in this survey will be necessarily a mixture of M supergiants in star forming regions in the interarm and galactic centre regions and M supergiants in the inner galactic arms.

We found 154 of 1146 late M stars with unique IRAS point source counterparts within 15 arcsec. 122 of the 154 stars have good flux qualities in the 12 and 25 μm bands. 112 of these, or 73 per cent of the late M stars (later than M4), have IRAS infrared colours in the range 0.7 < m12 − m25 < 1.6. Only two stars out of 122 have infrared colours redder than 1.7.

An infrared colour - MK spectral type diagram of optical M giants, M Miras and M supergiants is presented. The area in the diagram with m12 − m25 > 0.70 and MK spectral type earlier than M4 is occupied by early type optical M supergiants. The region of spectral type later than M4 is occupied by optical late M giants (Mira variables) and late M supergiants. The area in the diagram with a colour range of 0.15 < m12 − m25 < 0.70 is occupied by optical giants (Mira Variables) and supergiants (M supergiants with blue companions and probably some M supergiants in the evolutionary stage pre or post M supergiants with large infrared excesses). Finally, the area in the diagram with m12 − m25 < 0.15 is clearly occupied by M giants without circumstellar dust shells. The colour distribution of the M giants, M supergiants and M Miras in the colour - spectral type diagram suggests that we can use the colour properties as search criteria for (i) early M supergiants with colours of m12 − m25 > 0.70, (ii) late M supergiants with colours of m12 − m25 > 0.70, (iii) M giants with m12 − m25 < 0.15, (iv) Mira candidates using IRAS point sources which are also identified as optical M stars.

Results for a near-infrared objective-prism survey for faint cool carbon stars in a Carina region centred at l = 290°, b = 0° are presented. A total of 37 identified carbon stars in area of about 16 square degrees were found, of which 4 are new discoveries. Accurate positions, IRAS identifications, infrared fluxes and colours, and associations of the stars in the sample axe given.

The approximately 130,000 HD stars between declinations −90° and −12° have been classified on the MK system. This large, consistently classified database has been used to examine the distribution of the stars in galactic coordinates by using Aitoff equal area plots. Both normal stars, grouped by similar temperature and luminosity types, and peculiar stars of various types, will be displayed. The plots will be published in the Astronomical Journal, rather than in these Colloquium Proceedings.

We describe a long term project to find faint, heavily-reddened, cool supergiants and carbon stars and to classify IRAS Point Sources within 6° of the southern galactic plane. Many new supergiants and carbon stars have been found, and thousands of IRAS Point Sources have had their spectral types determined.

The combination of the excellent large-field imaging capabilities of Schmidt telescopes and of prisms covering the full aperture has made an impact on stellar, galactic, and extragalactic astronomy far out of proportion to the numbers of such telescopes. I discuss some of the milestones in the continuing development of this combination with a view to signposts of the future.

About 1300, 60 and 70 Herbig-Haro candidates have been picked up in the Ori A/L1641, Ori B/L1630 and NGC 2264/Mon OBI regions, respectively, on deep Schmidt plates. The contrast enhancement and unsharp masking technique has been applied simultaneously. Unsharp masking applied to an objective-prism Schmidt plate for the Carina Nebula region has yielded the detection of 38 Hα emission stars, of which 13 are new findings.