We have developed an astronomical imaging system tailored to our search for gravitational microlensing by compact objects in the halo and disk of the Galaxy. The challenge of detecting rare microlensing events is to monitor ∼ 10 million stars per night and distinguish genuine events from other sources of variability. The Large Magellanic Cloud and the Galactic bulge provide the high surface density of resolvable stars necessary for this task. A dedicated 50 inch telescope at Mt. Stromlo Observatory has been producing science data since the fall of 1992. Our system incorporates eight 2048 × 2048 CCDs into two focal planes for simultaneous imaging in two passbands (4500–6300 and 6300–8100 å). Each focal plane consists of four ‘edge-buttable’ CCDs in a custom mounted 2 × 2 array. The 0.62 arcsecond pixel scale (15 μm) yields a 40 × 40 arcminute square field of view in each frame. A sophisticated point spread fitting photometry package extracts up to 600,000 useful magnitudes per color per frame. The data collection rate we need is obtained by simultaneously reading out all sixteen CCD outputs (two per chip) at 34 KHz with 16 bit digitization. With exposure times of 150–300 seconds and a 70 second readout time we can collect up to 100 fields per night. These rates are designed to allow us to detect or rule out massive compact halo objects (MACHOs) in the 10−6–101M⊙ range.

It was realised very early in the development of the ESO 16 metre equivalent Very Large Telescope (VLT) that wide-field imaging is too complicated and costly to implement on the VLT itself and should be done with a smaller telescope.

The Hitchhiker camera performs CCD imaging of an off-axis field on a 4 m telescope in parallel with the normal on-axis scientific programmes. Using a dichroic beam splitter it images in two colours simultaneously, obtaining deep images in random fields suitable for survey work. Recent research projects have given particular emphasis to studies of faint galaxies and we present new results on the association of faint blue galaxies with candidate giant galaxies.

At most research telescopes, the physical size of CCDs currently still restricts the accessible field-of-view. However, for galactic as well as extragalactic work a field significantly larger than the typical 15′ is needed to study objects with large angular extent. In particular, this is desirable for objects that are well studied in other wavelength regimes such as the radio or FIR. High quality surface photometry of structures ≥ 40′ can be obtained by using CCDs with telescopes of short focal lengths.

The Gothard Astrophysical Observatory of Loránd Eötvös University was founded in 1881 by Eugene von Gothard, the first astronomer in the world who took a photo of the central star of Ring nebula. After nearly 80 years interregnum, the observatory was revitalized by Eötvös University in 1992 and its equipment is used both for education and for research.

Unique in the regime of wide-field astronomy is the multi-object spectroscopy system ‘FLAIR’ developed for the UK Schmidt Telescope (UKST). The current system can perform simultaneous observations of ∼ 90 objects across 40 sq. degrees of sky. FLAIR has given a whole new platform for performing astronomical observations with a Schmidt telescope in a non-photographic role. The system is simple to operate, highly stable, easy to interchange with standard photography and outclasses single-object spectroscopy systems on 2.0 m class telescopes for many types of observation. The system has continued to be developed to enhance its flexibility, robustness and versatility, culminating recently in the commissioning of new fibre feeds and formats. The facility to observe independent standard stars, and the capability of observing objects in two UKST fields in a single night has recently been demonstrated. FLAIR is a powerful, cost-effective addition to the instrumental repertoire of the Anglo-Australian Observatory in a way that was not even remotely envisaged when the UKST was built.

We have carried out wide field imaging observations in the near-infrared (J, H and K′ band) with a large format array camera attached to the prime focus of the 105 cm Schmidt telescope at Kiso Observatory. The image resolution, limiting magnitudes and the effect of thermal radiation are discussed.

The start of a general plate measuring facility at ESO was made in 1974 with the purchase of an OPTRONICS S-3000 machine placed at the ESO headquarters in Geneva. The facility was complemented around 1977 by a one-dimensional GRANT Series 800 Comparator previously used by ESO Santiago and finally by the acquisition of a PDS 1010A microdensitometer installed in 1979. After the ESO headquarters were moved to Munich in 1980, the measuring machines were reinstalled in the basement close to the ESO plate vault. Due to the declining usage of Coudé plates, the GRANT machine was taken out of service in 1988.

With the first demands to the LITE-project being available in summer 1992, it was obvious that the known systems such as Slevogt, Schmidt or Ritchey-Chrétien-Cassegrain did not offer an attempt at a solution.

The desire of astronomers for wide field telescope systems which surpass the RCC (1:8 max. 1.5 degree) in light gathering power and field of view are relative concrete today. For this type of telescope, detectors planned ARE CCDs in multichip arrangement.

In the last three years the author has developed a number of diffraction limited optics. Some of these are the contents of this paper.

It is an honour for me to be able to present this review of photography in wide-field astronomy. Let me begin by assuring this distinguished audience that this talk is not some sort of sentimental tribute to a redundant technology. Although photography may be the oldest way of accurately recording images of stars and galaxies it is still the most powerful tool which we possess for surveying the sky on the world's large Schmidt telescopes. Indeed, if the full promise of Tech Pan film is realised (and there will be more on that subject from Dr. Parker later today), photography in its ‘old’ age may extend in its usefulness well into the next century. So, far from being on its last legs, photography is just reaching its maturity, though not without something of a mid-life crisis.

This is probably the first astronomical meeting with a serious photographic content where Kodak has not been represented. We had invited Gordon Brown who was once responsible for the scientific imaging market to come and talk to us about the availability of spectroscopic emulsions. However, I was told the Company no longer has a person responsible for scientific plates, a fact which I interpret with some foreboding and a great deal of sadness. It therefore falls to me to fill this part of the program with a statement that has been approved, or at least not contested, by Eastman Kodak.

Kodak Technical Pan (Tech Pan) emulsion is an extremely fine grained, high resolution, panchromatic negative film with extended red sensitivity. It has been produced under this name since about 1980 (Kodak P–255, 1981) and is available on Kodak's Estar base in a number of thicknesses and sizes. The thick ∗∗base Tech Pan is designated 4415 and has been used with great success by the amateur astronomical community for many years (e.g. Martys 1991). Its astronomical potential was recognised early by Everhart (1981). However, tests at professional telescopes (e.g. West et al. 1981) and early sensitometer tests at the UK Schmidt Telescope (UKST) in 1981 and 1987 were discontinued when the glass and film samples did not respond well to normal hypersensitisation techniques. These and other difficulties led to a lack of interest among the professional astronomical community until quite recently (Russell et al. 1992; Parker & Malin 1992). The first successful use of 14 × 14 inch hypered Tech-Pan 4415 film in the UKST was in March 1991. Films were obtained which exhibited excellent image quality and resolution. Furthermore, in good seeing these appeared to be about 1 magnitude deeper than the equivalent IIIa-F emulsion on glass but with considerably lower grain noise. This result was achieved because two main problems associated with Tech-Pan and film use in the UKST have been resolved. These were:

1. 1) obtaining Tech-Pan film with long exposure speed sufficient for deep astronomical photography (i.e. reduction of low intenstiy reciprocity failure);

2. 2) overcoming the practical difficulties of mounting large-format flexible film at the UKST's curved focal surface.

The recent years have seen a clear trend in observational astronomy towards digital detectors, but they are only able to cover sky fields which are significantly smaller than what is possible with photographic plates. In consequence, there has been a tendency to concentrate on small sky areas and individual objects. Nevertheless, many large-scale structures can only be well comprehended if the observed fields are much larger than such CCD-frames. Similarly, the use of more than one passband adds important information for a better understanding of the nature of large structures. We demonstrate this by showing here a two-field composite of IC 1396 (Palomar/ESO Atlas), and a four-field composite from the ESO R-Atlas, covering an area of more than 100 square degrees around IC 4628 in Scorpius/Ara.

For this work, we used the red plates of POSS II fields 340 and 115 which show the impressive wide-field areas around the IC 1795/1805 complex (Plate 1) and Gamma Cygni (Plate 2). The applied photographic method aims at the simultaneous enhancing of very faint features and compression of the dynamic range, so that all features become visible on the same print.

This paper continues the investigations carried out at the Royal Observatory Edinburgh into the microspot problem affecting Kodak Spectroscopic plates taken with the UK 1.2m Schmidt Telescope (UKST) at Siding Spring Observatory (SSO). Over 10,000 plate inspections have been made since the previous report. Analysis of all the available data shows that UKST plates on IIIa- emulsions processed up to January 1991 continue to show evidence of microspot contamination. Various changes to the processing procedures are listed and the effects on spot formation are analyzed. The effectiveness of Rapid Selenium Toner in the original processing line and post-processing is discussed.

As we know, the first report on photographic plate hydrogen hypersensitisation (hypering) is dated 1871 (U.S. Patent No. 113327, April 4 1871, see Janusonis et al. 1978). A new interest in the topic appeared in the 1930s, after the work of Robert Kozlowsky at Agfa Wolfen. Kozlowsky was the inventor of gold sensitization. In the 1950s in Russia the action of hydrogen on thick nuclear emulsions was also studied (Tschernyavsky et al. 1962). Strong fogging, especially at increased temperatures, was observed.

Ground-based wide-field optical astrometry is in a state of technological turmoil. The photographic plate appears to be an endangered species, and the best alternative, the charge coupled device (CCD), is not ready to replace it This discussion presents various issues related to this inevitable transition from plates to CCDs, and suggests areas where research is needed before the appropriate CCD detectors can be designed.

The Space Telescope Science Institute (STScI) continues with its programs of digitization, cataloging and data distribution. These were defined earlier, at the Geneva and the Edinburgh workshops (Jaschek 1989; MacGillivray & Thomson 1992), and this report, by necessity of space, is incremental upon them.