A new controller concept based on transputer modules (TRAMs) and Digital Signal Processors (DSPs) has been developed at ESO. The Array Control Electronics (ACE) can handle single CCDs or CCD mosaics with 1 to 64 outputs and with up to 256 clocks with software programmable independent high and low voltages. The same basic concept will be used for slow scan scientific and fast scan auto guiding/wave front sensing applications. While the transputers are mainly used for data acquisition, communication and supervisory tasks, a DSP with very simple external logic performs the time-critical CCD clock pattern generation. The low noise, high speed clock driver with built-in telemetry is designed for highest operational safety. A newly designed video processor board has four video channels each with its own 16-bit ADC. ACE can easily be interfaced to various types of host computers like PCs, Unix workstations or ESO's VME-based LCUs (Local Control Units with VxWorks real-time operating system).

The GALILEO telescope requires a flexible detector controller that allows one to drive single and mosaic CCDs in different modes of operation. The CCD controller can be divided into two main parts: the preamplifier, located close to the cryostat and the other modules, the Sequencer, the Bias generator, the Clock driver, the Preamplifier and the Correlated double sampler, located into a rack and connected together via a CCDC-BUS.

We describe a versatile array controller developed at RAL and SAAO. The original concept was due to Waltham, van Breda and Newton (1990). A Transputer-based microcomputer forms the heart of the device.

A family of virtual phase (VP) CCD array image sensors for various industrial and scientific applications has been designed, fabricated and tested. All share the common concept of a “2.5-phase” photosensitive cell, combining the advantages of known “1.5-phase” VP devices (increased quantum efficiency, especially in the UV, and radiation hardness) with the simpler fabrication process and extended functionality of three-phase devices.

Time-series high-accuracy photometry is very important for research in stellar variability. For a long time photometry made by a photomultiplier was the only instrument for high precision stellar photometry. To overcome the atmospheric variation and instrumental problems, we must choose at least one stable star as a comparison star and move the telescope quickly between the targets. So the real efficiency is very low and one only can do it on photometric nights. To overcome this limitation, since 1989 we began to cooperate with the team of the STEPHI network. We used the Chevreton four-channel photometer which can observe the variable, two comparison stars and a chosen sky background simultaneously. The multi-channel photometer is much better than normal single channel photometer as we can see from the several STEPHI results. Now the very high quantum efficiency CCD becomes more and more popular, so we are trying to change to use CCDs. Here we give some general description of a large field high accuracy bright star CCD photometer being prepared for the Beijing Astronomical Observatory (BAO).

CCD-shutters take some time to open and close. This results in a difference between the recorded and real exposure times. The pixel-to-pixel pattern δ(x, y) in which this difference varies depends on the characteristics of the device. These timing errors affect photometric measurements in two ways: directly, since the recorded exposure time is not the real one, and indirectly, via the flatfielding process, because the shutter effect is mixed up with the flatfield pattern. The direct effect may be negligible when exposure times are long. The indirect effect is present irrespective of the exposure times of the frames, if flatfield exposure times are short.

The first century of non-visual astronomical image detection in Hungary was devoted exclusively to photography. The most famous Hungarian astronomers and astrophysicists of the last century were the pioneers of astrophotography too. The very first exhaustive description of photography as a scientific method was the one by Konkoly-Thege about astronomical photography in 1887. In his book one can find some interesting images printed of the plates taken by his friend and colleague, the enthusiastic astrophotographer J. Gothard, who was the first to demonstrate that the well-known bright planetary in Lyra (M 57 or the Ring Nebula) contains an extremely faint central star. His discovery, which opened new fields for astrophysics, was contested for a long time because his foreign contemporaries were unable to repeat this feat of arms.

A CCD-system is proposed to maintain the alignment of an optical system of a large space telescope during ground tests and after launch. The system is able to detect alignment errors resulting from displacements of the main and secondary mirrors of the telescope and also from the tilts of these mirrors. Computer simulations have been performed to determine the sensitivity of the system to the displacements and/or the tilts. Different sources of errors have been also explored on a working stand; and the main requirements to the elements of the system have been determined. The system is to be installed on the space telescope “Spectrum-UV”. It can be also used in ground-based telescopes in a quasi-real time mode.

The Zverev photographic vertical circle (PVC) of the Pulkovo observatory is in the process of modernization. The features of the vertical circle are:

1. a) Maksutov mirror-lens optical system with small aberrations and wide passband: aperture: 20 cm, focal length: 200 cm, focal scale: 103 arcsec/mm.

2. b) Very compact instrument: 140 cm total length, 60 cm — tube.

3. c) Wide field: 25 × 25 mm = 40′ × 40′. Wide-field imaging can be combined with meridian observations.

4. d) Easily-reversible instrument: reversing takes less than 30 seconds.

5. e) Two divided vertical circles of glass. Photoelectric circle reading microscopes.

6. f) Photographic micrometer in focal plane. This will be changed with a CCD micrometer.

A working model of an ocular micrometer has been designed for the MAHIS (Meridian Automated Horizontal Instrument by Sukcharev). An optical scheme of the micrometer includes the following devices:

1. a) Artificial light marks in the focal plane of the objective. The marks have an increased sharpness and have a stable scale factor under defocusing. An amplitude-phase grid illuminated by coherent light from the second main point of the objective is used to make the marks.

2. b) The observed stars and artificial marks are imaged on the CCD chip by means of an additional objective. This objective also corrects chromatic aberations of the main objective.

3. c) A concentric meniscus is used to compensate for the chromatic refraction of the atmosphere. The meniscus center of curvature coincides with the center of the system's pupil image. In this case the compensation is equal at all points of the field of view.

4. d) The possibility of measuring the normal attitude of the flat mirror relative to the main instrumental plane during each observation is discussed. For these purposes there needs to be a holographic grid on the mirror surface, an artificial zenith or nadir horizon and an autocollimated source of light in the focal plane.

5. e) Laboratory investigations of a working model of a CCD camera are being carried out and the basic software is being developed. This work is planned to be finished in the autumn of 1994. The CCD matrix ISD 011A (NPO “Electron”, St. Petersburg, Russia) 512 × 512 pixels, with pixel size of 16 × 16 mkm is used. The noise is 5 electrons/pixel/sec when the temperature is −40° C (thermoelectric cooler).

A new infrared meridian instrument is being developed at Pulkovo Observatory. The main purpose of the instrument is to extend the fundamental coordinate system to the K-infrared waveband and to faint stars at visual and I-wavebands. The instrument has a 30-cm primary mirror made from astrositall. An intermediate focal plane is used to introduce luminous reference marks. One can obtain autocollimated images of the marks at the intermediate focal plane with the use of a polished chamber located around the central hole of the primary mirror. The secondary mirror of the telescope forms images of the marks and of their autocollimated counterparts and passes them to the plane of a photodetector (Fig. 1.). The luminous marks give a reference frame for the measurements. These measurements are not affected by displacements of any optical unit placed after the intermediate focal plane or by displacements of the detector. The measurements are done relative to the coordinates of the average between positions of the luminous mark and its autocollimated image. Any small constant difference between the center of curvature and the optical axis position can be determined in the laboratory.

The Array Controller (Arcon) developed at CTIO is a flexible and extendable system for acquiring astronomical data from a wide variety of optical and IR detectors. It has been designed from the outset to support expansion to more demanding applications such as large CCD mosaics. In its minimum configuration it can read a quad-readout CCD through all four amplifiers simultaneously.

Electron-Bombarded CCD (EB-CCD) image intensifiers, based on the primary photoelectron multiplication effect in the CCD substrate, provide a number of advantages over routine intensified CCDs, optically coupled with the output of conventional image intensifiers. Despite this fact, there are no commercially available intensified EB-CCD imagers, though many CCD and image intensifier's manufactures put great efforts to design devices of such kind. This paper briefly reviews the results of more than a decade of work in the field of intensified EB-CCD imaging devices in the “Electron” National Research Institute, Russia's leader in optoelectronics.

It is incumbent upon ESO to ensure that its CCDs perform according to advertised specifications (Abbott 1994). We describe a systematic, regular testing program for CCDs which is now being applied at La Silla. These tests are designed to expose failures which may not have catastrophic effects but which may compromise observations.

The CCD we use is TC215 manufactured by TI, Japan. The pixel size is 12 microns square. It is a virtual phase CCD which has a peak QE of 60% at 700 nm and 15% QE at 350 nm. It is commercially available in a package, which is too big to meet our requirement for CCD spacing. We therefore put the CCD in a specially made compact package. Each chip is mounted on a machined ceramic spacer whose thermal coefficient is matched with that of the CCD package. We glue each CCD chip on the spacer under a microscope to measure YHE x − y position and height. Then we screw the CCD chip + spacer on a copper motherboard with the help of the gauge which has a planned grid with a good accuracy. The alignment accuracy we can get with such set-up procedures is an order of 5 microns (< 0.5 pixel) in the horizontal direction and 10 microns in the vertical direction.

The 0.5m refracting telescope of the Van Vleck Observatory has been active in the determination of trigonometric parallaxes since its first observations in 1922. Its lenses were ground by C.A.R. Lundin of the Alvan Clark Co. for photographic use. Coma was minimized across the field and vignetting was also kept to a minimum. Partly as a consequence the focal curve is very steep in the blue and green regions of the spectrum, as is shown in Fig. 1. A Wratten No. 12 minus blue filter is used to filter out all wavelengths to the blue of about 5200 å. The region between 5200 å and 6000 å is very flat with the focal plane varying over a range of about one millimeter. Towards the red region it steepens, although not enough to impair images on photographic plates of emulsion types 103a-D and IIIa-F, the two in widespread use in recent years.

The CIDA visual refractor of 65-cm aperture and focal length 10.5 m, has been used extensively for position determinations on photographic plates. The combination of Kodak D plates and a yellow filter permit an almost perfect adaptation to the focal curve of the telescope. It appeared of interest to test whether the telescope could be used for astrometric purposes with a CCD detector. As is well known, the spectral sensitivity of these detectors extends well into the infrared where the images formed by the telescope optics will be far out of focus. The blue spectral region where this would also be the case can easily be cut off by a yellow filter. There are no filters which would produce a similarly sharp cut-off towards the red region. On the other hand, given the small field covered by a CCD, the displacement of the red out-of-focus image with respect to the center of the visual image might be negligible. Recently obtained accurate positions in the area of the Perseus Double Cluster made this field suitable for the test of this possibility.

An application of the Classical Laplacian Method and new Pulkovo AMP-method for current asteroid orbit determinations is given. The CERES software package created at the Institute of Theoretical Astronomy (Russia) was applied to calculate (O-C)-differences for 200 numbered minor planets observed irregularly and quasisimultaneously in 1993 by CCD as well as by photographic techniques at 25 observatories (ESO, SERGA, Kitt Peak etc.). The accuracy of the observations was estimated by means of the standard error of the average (O-C) differences for each type of observation obtained by each telescope. As a whole the CCD-observations of the numbered minor planets are considerably more precise in comparison to the photographic ones. Some results are given in Table 1.

At the start of CCD observations one must investigate the metrological properties of the complex instrument: optics + CCD. One needs a densely spaced set of stars with precise coordinates and magnitudes. We first used the Pleiades catalogue by Eichhorn et al. (1970). Experimental observations were started at Pulkovo in 1993 using a very small refractor (D = 100 mm, F = 712 mm) equipped with a CCD ISD015A (520 × 580 pixels, 18 × 24 microns). The focal length of our astrograph provides an angular field of view of 45 × 67 arcmin (angular scale is 5.2 × 7 arcsec/pixel). With different exposures we can observe all stars with magnitudes from 2 to 16. The first observations were made to evaluate the accuracy of our positional and photometric measurements. Unfortunately, it appears that the catalogue of the Pleiades by Eichhorn is not good enough for this purpose because its epoch is very far from that of our observations and proper motions were not provided for the majority of the stars. The internal precision of our measurements (0.1–0.3 arcsec) allows us to determine the corrections to the stellar positions by Eichhorn et al. (1970)

We discuss CCD UBVRI and NICMOS3 JHK observations of the young open cluster Westerlund 2, with emphasis on both reduction techniques and absolute calibrations.