Instrumentation presently in use for low resolution, digital spectroscopy on 1 meter class telescopes at three observatories - Lick, Kitt Peak, and Cerro Tololo - is reviewed. A detailed comparison is made between the performance of a typical two-dimensional photon counter, the “2D-Frutti”, and currently-available CCDs. Prospects for further detector advances center on large-format, low-noise, uvsensitive CCDs.

We review the spectral classification work with low dispersion. It is mainly concentrated on the MK-System. First we summarize the original properties of this system, its evolution and its present properties. We describe the MK Process and emphasize its importance as a tool for future research on spectral classification. In the third section we comment briefly about the instrumentation and the techniques used in spectral classification work and finally we mention a list of research programs that can be undertaken with a 1m-telescope and a good spectrograph.

This paper comments on the growing use of cassegrain échelle spectrographs for high resolving power astronomical spectroscopy over the last two decades. Some of the theoretical and practical advantages of échelle spectrographs are outlined, as well as some of the problems that arise in their use. Design parameters of some recent échelle spectrographs in various observatories are summarised. A novel use of échelle spectrographs without a cross-dispersing element for radial velocity spectrometry is proposed. The design parameters of a fibre-fed échelle spectrograph that will achieve a resolving power of about 7 × 104 with a 2 arc second input from a 1m telescope are outlined.

The complete radial velocity curve has been determined with CORAVEL for many pulsating stars of various classes: cepheid stars in the Galaxy and in the Magellanic Clouds, RR Lyrae, δ Scuti and SX Phoenicis stars. These measurements allow the determination of the radius variation and of the surface acceleration of these stars. In addition, the mean stellar radius of many of these stars has been determined by applying the Baade-Wesselink method.

Systematic surveys of definite groups of binary or multiple stars are in progress with CORAVEL in order to determine the distribution functions of the orbital parameters. The eccentricity distributions for the binaries in the open clusters Pleiades, Praesepe, Coma Ber and Hyades are presented and their dependence on the physical processes (star formation mechanisms, mass exchange, tidal circularization, dynamical evolution) is briefly discussed.

The basic requirements for high precision spectral line profile measurements are reviewed, with the observatory at the University of Western Ontario serving to illustrate several of the points.

The methods by which abundance analyses can be undertaken, especially with the growing use of high quantum efficiency digital detectors, are reviewed. The importance of the differential curve of growth technique is discussed, followed by a review of some recent results involving both late-type dwarf and giant stars. These include (1) the F and G dwarf abundance analyses of the elements sodium through nickel, which show an important differentiation between stars belonging to the young and old disk populations, (2) the possibility that departures from local thermodynamic equilibrium can effect sodium and aluminium abundances in late-type giants and supergiants and (3) that significant differences exist between the abundances of carbon, nitrogen and oxygen in old disk and young disk giant stars. Finally, the implications of these abundances in terms of stellar and galactic evolution are briefly addressed.

Observations of visual binaries made with the 1.2-m telescope and coudé spectrograph at Victoria are described, with particular emphasis on their value as tests of evolutionary calculations.

The bright star δ2 Lyr has been observed photoelectrically in the V and B pass bands for three years. The star is a long period variable with an amplitude of 0.2 mag and a period of 83 days. Light changes are coupled with small range velocity changes. On some well-exposed spectrograms the emission features of the H and K lines of CaII appear.

Heterodyne spectroscopy combines high instrumental transmission with virtually unlimited spectral resolution. For 250 K bodies like Mars and Venus resolution is limited to 107 (= 30 m/s) because of photon statistics whereas for solar measurements the cm/s velocity range, desirable for study of solar oscillations, is feasible. Since a single heterodyne receiver is conserving its etendu, smaller collecting area results in larger field of view. The signal remains unchanged as long as the source is large enough to fill the beam. For Mars, Venus and the Sun heterodyne observation with 1m aperture is competitive.

The stellar radial velocity (RV) observations collected during the first eight years (1976–1984) of operation of the Fick Observatory photoelectric RV spectrometer have been tabulated for publication (Beavers and Eitter, 1986). Included are 16,000 observations of over 2,000 late-type stars. For these observations at the coudé focus of the 61 cm telescope the velocity zero-point is virtually the same as that for the early Lick radial velocity survey (Campbell and Moore, 1928), i.e. Lick-Fick = −0.08±0.08 km/sec. The zero-point comparison for DAO spectrometer measurements is DAO-Fick = −0.54±0.05 km/sec. During the last four years of this study the error of the “high quality dip” observations is ±0.8 km/sec. Thirty-three of these stars have been selected for use as future bright (m < 7.0) velocity standards at Fick Observatory.

A fast astronomical spectrometer is described using commercially available photographic lenses and a CCD detector. The size and weight of the instrument have been kept to a minimum to allow it to be used on telescopes as small as 0.6m.

A spectroscopic survey of visual binaries with known orbital elements has been carried out with the radial velocity scanner CORAVEL at the Haute-Provence Observatory, since 1977, (Baranne, Mayor, Poncet, 1979). This survey of more than 100 visual systems, selected from Dommanget's catalogue (1967) (see also a new edition 1982) was first devoted to the determination of stellar masses. Several multiple systems were detected and have permitted also a study of the structure of triple systems. We have detected and measured in particular a class of triple systems with radial velocity variations of small amplitude. Taking advantage of the high resolution and high signal-to-noise ratio accessible with the cross-correlation technique, such small amplitude radial velocity curves are sometimes derived only through the change of width and shape of the cross-correlation function. Let us recall that the cc-function of a SB2 (or SB3) system is only the weighted sum of the individual cc-functions (Mayor, 1985). This property of the cross-correlation combined with the linearity of the detector allow a very simple analysis of blended dips. The full width at half depth of the cross-correlation dip is about FWHD = 16 km/s (in absence of noticeable rotation). Analysis of blended systems allows a good determination of the two individual velocities if the difference |vr1 -Vr2| is equal or larger than about 0.15 *FWHD (about 2 km/s).

AB Aur = HD 31293 = BD + 300741 = MWC 93 = HRC 78n is one of the brightest members of a class of pre-main sequence objects introduced by G. Herbig in 1960. The star is characterized by a spectral type of AOVe, L/L⊙ = 70, mv = 7.2 mag, v sini = 140 km/s, and d = 140 pc. Assuming a stellar radius of a main sequence dwarf R/R⊙ = 3.0, one can estimate the rotational period to be on the order of 28 hours if we see the system edge on. Previous work (Praderie et al. (1985) and Finkenzeller (1983)) has focused on high resolution spectroscopy and shown that AB Aur is subject to short term variations. Finkenzeller's observations have indicated that the emission features can disappear completely within a day. Praderie et al. found evidence of a rotational modulation (45 ± 6 hours) of the MgII λ 2795 and FeII UV lines which is interpreted as due to a non-axisymmetric wind interacting with the outer atmosphere.

A photoelectric radial velocity spectrometer has been in operation for several years at the coudé focus of the 1.2m telescope of the Dominion Astrophysical Observatory (DAO). The design of this instrument has been described by Fletcher et. al. (1982) and by McClure et al. (1984). These papers discuss the similarities and differences between this spectrometer and others of its type such as that constructed by Griffin and Gunn (1974) at Palomar. The spectrum mask in the present instrument consists of more than 700 transparent slots on an opaque background, representing the spectrum of a K giant star, plus a few slots to coincide with the argon lines in a cadmium-argon discharge tube for use in obtaining comparison arc velocities. By progressively tilting the slots an appropriate amount along the mask and scanning by moving the mask relative to the stellar spectrum at 45° to the dispersion it is possible to retain a spectral match at non-zero velocities. The masks are produced using a standard measuring engine modified with stepping motors controlled by a computer to position and tilt the slots. Since guiding errors are our major source of error we hope to make a significant improvement in this area in the following manner. By inserting an image rotating prism behind the slit a 180° rotation of the slit will occur when the prism is rotated. Although this has not yet been tested, it is hoped that by making this rotation every few scans the effects of guiding errors due to uneven illumination of the slit and collimator will be vastly reduced.

Changes in Ti0 band strengths correlate well with the brightness changes of α Orionis, thus supporting the hypothesis of Schwarzschild that the irregular luminosity variations of red giants are due to temperature changes in a few extremely large convective elements on their surface.

EG&G Princeton Applied Research produces a Reticon detector system intended for laboratory applications. However, current versions of the system are well-suited to astronomical observations at observatories with modest financial and technical resources.

The detector inputs are intensified by microchannel plates, fiber-optically coupled to a 1024-pixel Reticon. Controller and readout electronics, and software for data pre-processing and graphical display are also available off-the-shelf, enabling the observer to put the system to use without a major development effort.

We have developed several detector systems for use in observational astronomy. These include a rapid scanning spectrometer (Jeffers and Weller, 1973), a rapid chopping spectrophotometer (Stiff and Jeffers, 1978) and an intensified, silicon vidicon detector for use either for spectrophotometry (Jeffers, Stiff and Weller, 1983) or direct imaging (Jeffers, 1982). These detector systems have been used for rapid variability studies of emission line strengths and profiles in Wolf-Rayet and Of stars (Weller and Jeffers, 1979; Jeffers, Stiff and Weller, 1985) and for low dispersion spectrophotometry of these stars (Jeffers and Weller, 1985). Here we report on the spectrophotometric performance of the intensified, silicon vidicon detector (RCA 4804H) when used with a low dispersion spectrograph.

A miniaturized spectrometer designed for mounting at the Cassegrain focus of a 40 cm telescope has been built and laboratory tested with promising results. The optical system consists of a slit, spherical mirror, and reflection grating in a Littrow configuration. The detector is a 128 element linear CCD cooled by an evacuated microminiature nitrogen refrigerator and interfaced to a microcomputer using direct memory access. Laboratory spectra of a mercury vapor discharge tube have been obtained and demonstrate 1 Angstrom resolution with low noise. The spectral coverage of about 100 Angstroms is suitable for measurement of stellar H-alpha line profiles, and it is anticipated that the instrument can be used to monitor bright Be stars.

We are making accurate observations of the change in Doppler shift of stellar absorption lines. The purpose is to detect the oscillatory reflex motion due to planets orbiting stars. The scrambling of incident light by an optical fiber and the stability of wavelength calibration by a Fabry-Perot etalon provide immunity to systematic errors. Selecting several echelle diffraction orders in the vicinity of 4250–4600 A, which are imaged on a CCD, about 350 points on the profile of the stellar spectrum are sampled by successive orders of interferometric transmission through the etalon. At 4300 A each interference order is 47 milliangstroms wide and the sample points are 0.64 A apart, causing distinct, widely-spaced monochromatic images of the entrance aperture to be formed in the focal plane of the camera. Changes in Doppler shift modify the relative intensities of these images, according to the slope of the spectral profile at each point sampled. To simplify operation and enhance sensitivity, the instrument is being operated as a null-measurement accelerometer, responding only to changes in radial velocity. With an argon emission line lamp the interferometer is calibrated to two parts in 100 million; this corresponds to ± 6 meters/sec in Doppler shift. These calibrations show instrumental variations of ± 27 meters/sec on a time scale of months; observations of stars are corrected for such changes. The internal repeatability of observations of the differential Doppler shift of Arcturus (K1 IIIb; B=1.19) is ± 6 meters/sec for each exposure of 600 square meter-seconds. These exposures are obtained in 15–20 minutes with a 0.9-meter telescope. The external repeatability (day-to-day differential accuracy) of nightly averages of stellar observations is ± 20 meters/second.