Instruments to study simultaneously the spectra of many objects in the field of view of a telescope can be made with the aid of fused silica fibers. The spectrograph at the 2.3m telescope of the University of Arizona has been modified for such operation, and is used routinely to investigate the dynamics of clusters of galaxies (Hill et al. 1981). The system presently in use locates up to 40 fibers in the telescope's Cassegrain focal plane, with the aid of plates previously drilled with holes in the configuration of the objects to be studied. Each field must be set up by hand by inserting fibers into a hole plate. An obvious improvement to this method would be to mount each fiber on a mechanical actuator, so new field configurations can be set up by remote control. It is our intention to make such a system with 32 fibers for the 2.3m telescope, over the next two years.

A combination of an array of small lenses together with fibre optics can be used to produce a high transmission spectrograph which can record the spectra of many image elements simultaneously. Such a design may play an important role in ground based observations preparing for the NASA-ESA Space Telescope programmes.

Spectrographs using plane aspherized gratings have excellent resolution over a wide field and require one less element than a conventional Schmidt or Maksutov camera. However, they are restricted to configurations where the grating is approximately normal to the camera axis.

Aspheric diffraction gratings have been produced by the elastic relaxation method. These gratings lead to more efficient spectrograph mounting arrangements since, for a wide field instrument of fast aperture ratio, a smaller number of optical surfaces are required. The UV-PRIM spectrograph is the first instrument of this type to have been constructed.

Direct photographic work over a large field (1°) at the prime focus of the classical Canada-France-Hawaii 3.6m telescope has been achieved with a very good image quality (less than 0.5” FWHM). The basic characteristics of the Wide-Field Corrector are presented. Our Wynne Corrector was in fact redesigned to have the last optical surface flat so that a transmission grating could be replicated thereon. This arrangement with only three optical elements locates the gratings at a maximum distance from the focal surface resulting in improved resolution over a one degree field. The C.F.H.T. grating-plus-lens, or “grens” has a brightness limit which is fainter than the Palomar Sky Survey.

This paper compares the two major types of catadioptric camera, viz. the Maksutov camera and the Schmidt camera, when used for astronomical spectroscopy in instruments dedicated to image tubes, diode arrays and similar types of detectors. The review is limited to the detailed description of systems with which the author has been personally involved, that is, they have either been made at RGO or represent RGO participation in external projects.

I wish to begin by saying a few words on an instrument which has been utilized thus far only to observe the sun, with a very small telescope of about 5cm diameter. This may appear to stand far away from the main topic of this meeting but in fact, the scientific program which is successfully being developed on the sun would be of major interest for stellar astronomy if it could be extended to at least a few bright stars. I will therefore describe also a possible extrapolation of an instrument to be used on the largest available telescopes for stellar observations.

A simple, low cost, television spectrometer has been constructed at the Crimean Astrophysical Observatory using an I-Isocon image tube for analog-digital recording of stellar spectra. High quantum efficiency (0.04) together with good accuracy (±0.3%) and repeatability are obtained.

One of the basic astrophysical problems is to search for and investigate brightness fluctuations of celestial objects at times comparable with the mean time between registered photons. With that end in view, a special mathematical formalism has been developed in recent years (Shvartsman, 1977; Pimonov and Terebizh, 1981; Plakhotnichenko, 1980).

The description of a speckle camera used with the BTA 6-meter telescope is given. Observational data recorded on photographic film are processed with a Fourier optical spectrum analyzer. Results of binary star measurements are presented. Analysis of short exposure images of a point source obtained with telescopes of various sizes allows the estimation of atmospheric parameters which are necessary for correct application of speckle interferometry.

We propose to develop a technique to achieve submillisecond of arc resolution on stellar objects. It uses the fact that the spectrum of the light emitted by such an object often changes across its surface either because of Doppler shifts, Zeeman splitting, abundance anomalies or changes in the stellar atmosphere. By an appropriately designed experiment using narrow band (0.5 – 1 Å) filters, it is then possible to obtain differences between the position of speckles in the stellar image when viewed in slightly different wavelengths. It is possible to determine these differences in the position of the speckles with an accuracy much higher than the speckle size itself using techniques which are already developed for binary star-speckle research. We propose to use the technique of “Differential Speckle Interferometry” to study stellar rotation, evolution of stellar systems, spectroscopic binaries, the mass-luminosity relation, and peculiar A stars.

Compared to speckle-interferometry, amplitude-interferometry has the following advantages:

1. (1) The amplitude of the object Fourier components is insensitive to both turbulence and telescope induced aberrations, permitting an accurate calibration of visibility curves,

2. (2) Interferograms are free from speckle noise, permitting a better signal-to-noise ratio on bright sources,

3. (3) Information can be retrieved from fewer exposures (including complete image reconstruction),

4. (4) Accurate visual measurements of stellar diameters and of the angular spacing of binary stars can be easily performed.

A high resolution interferometer (60cm maximum path difference) for use from the visible region to 5μm has been designed and manufactured at Meudon Observatory to be part of the instrumentation of the Canada-France-Hawaii Telescope. The considerations which led to the choice of the interferometer being operated at the Cassegrain focus, and the design features which allow this to be achieved, are outlined.

This detector has been in use since 1977. Following Labeyrie (1977), it consists of a microchannel plate electrostatically focussed intensifier (TH 9304) coupled by fiber optics to an SIT camera (TH 9655), these parts being manufactured by THOMSON-CSF (FRANCE). The diameter of the S20 photocathode is 25mm but the silicon target is only 18mm wide. The scanning electronics are conventional. The detector is cooled to -5°C, the photocathode being in a dry nitrogen chamber. The system has been described by Boulesteix (1978).

A photon-counting astronomical instrument for optical observations with nanosecond time resolution is being developed to observe the statistical distribution of photons in time. The purpose of this ‘quantum-optical spectrometer’ is to measure quantum-statistical properties of the photon gas and to study the physics of radiative deexcitation. The amount of photon bunching in time contains information on parameters such as the fraction of stimulated emission and the degree of frequency redistribution that the light has undergone.

This is a summary of the meeting “Solid State Imagers for Astronomy” held at the Harvard-Smithsonian Center for Astrophysics in June 1981. The main emphasis of this report is a comparison of the performance characteristics of the CCD detectors now in use.

The Multi-Anode MicroChannel Arrays (MAMAs) are a family of photoelectric, photon-counting array detectors that are being developed specifically for use in instruments on space-borne and ground-based telescopes. In this paper we review briefly the construction and modes of-operation of the MAMA detectors and describe the current development status of the different detector systems.

Since 1978 we have been using photon-counting Reticons for spectroscopy at Mt. Hopkins. With these detectors we have accumulated approximately 50,000 exposures, resulting in nearly 10,000 reduced astronomical spectra. This paper describes the performance of the detectors, discusses some of the procedures we use for remote observing, outlines the magnitude of the data-handling problem, and gives a few examples of recent results.