The Macho Collaboration uses a dedicated 1.27-m telescope (The Great Melbourne Telescope) at Mount Stromlo to make photometric measurements of tens of millions of stars per night searching for the gravitational microlensing signature of MACHOs in the halo and disk of the Milky Way. A prime focus corrector and dichroic beamsplitter provide red (6300–7800 å) and blue (4500–6300 å) foci with one degree fields. A two by two mosaic of 2048 × 2048 pixel CCDs in each focal plane provides simultaneous images of 0.5 square degrees. By August of 1994, more than 20,000, 32 Megapixel images will have been collected of fields in the Large Magellanic Cloud (LMC), Small Magellanic Cloud and the bulge of the Milky Way. We have implemented an online analysis system which produces photometric reductions of a night's data (five Gbyte of images) within 24 hours. This system allows us to identify and follow interesting events in real-time. In this search, we have identified more than 60,000 variable stars, and a preliminary analysis of their types and distribution will be presented. Microlensing events toward the LMC and the bulge have been discovered and detection efficiencies are being calculated to constrain the MACHO content of the Milky Way's halo.

The UCLA two-channel IR camera has been used to perform crowded-field photometry in two distinct classes of extragalactic objects. DAOPHOT was used to reduce images of M 33 and provide JHK color-magnitude diagrams of over 1,700 stars. Galaxy photometry in crowded clusters, e.g. Abell 370, was obtained in JHK and analyzed using FOCAS. In both cases, extensive reductions were performed using synthetic aperture photometry for comparison. Methods and results are summarized.

The Strömgren four-color system is well suited to the measure and analysis of horizontal-branch stars. The increased accuracy of the CCD photometric system and the ability to measure fainter stars in very crowded regions make the combination of the CCD system and four-color photometry an excellent one to study horizontal-branch stars in globular clusters.

The Vilnius photometric system, consisting of seven passbands at 345, 374, 405, 466, 516, 544 and 656 nm makes it possible to determine spectral classes (or temperatures), absolute magnitudes (or surface gravities), metallicities and peculiarity types for stars of all spectral types in the presence of interstellar reddening (Straizys 1977, 1992a, b). This makes the system very useful for the determination of the physical parameters of stars which are too faint to be studied by spectroscopic methods. The system is especially effective when used with CCD detectors which combine a wide field, high sensitivity and high photometric accuracy.

We present a detailed analysis on the extent of the errors in the intensity measurements of low signal-to-noise narrow emission lines. Our first goal is to determine a model for the probability distribution function (p.d.f.) associated with the measured intensities of a line characterized by its signal-to-noise ratio. Our final purpose is to provide an error domain: — for the measured signal-to-noise ratio of an observed line; — for the ratio of two lines in terms of their signal-to-noise ratios, and eventually (with the knowledge of the noise energy) to get errors on the corresponding intensities and intensity ratios.

He I, λ 10830 å observations of late-type stars provide valuable information about the chromospheric and low chromospheric-coronal transition regions. High resolution measurements of the helium λ 10830 å line profile offer a convenient way to survey the coronal emission of the Sun as a point source, as well as a variety of stars (O'Brien and Lambert, 1986, Shcherbakov and Shcherbakova, 1991).

We have developed algorithms for the construction of a simulated globular cluster, as it would appear on a frame obtained with a perfect CCD. This has allowed us to compare the absolute errors in the photometry of two different programs, DAOPHOT II (Stetson 1991, 1994) and SPS (Janes and Heasley 1993), with a special emphasis on criteria for selecting stars with the best photometry.

We have constructed a computer model for simulation of point sources imaged on CCDs. An attempt has been made to ensure that the model produces “data” that mimic real data taken with two-D detectors. To be realistic, such simulations must include randomly generated noise of the appropriate type from all sources. The synthetic data are output as simple one-D integrations, as two-D radial slices, and as three-D intensity plots. Each noise source can be turned on or off so they can be studied independently as well as in combination to provide insight into the image components.

3D is a next-generation near-IR spectrometer developed at the MPE which offers, in a single integration, the opportunity to image an 8″ × 8″ field across almost the entire K-band at a simultaneous spatial resolution of 0.″5 wide strips which are then aligned optically on top of each other forming a single long slit. This long slit is then used as the input for a grating spectrometer which images it onto a two dimensional detector array. Each detector row then represents the spectrum of one spatial element of the two dimensional field of view. The central part of the optical system is the image slicer which is made of two complex plane mirror systems consisting of 16 segments each. The detector is a NICMOSIII HgCdTe array with 256 × 256 pixels. In the spectral domain the spectrometer provides a resolving power of R = 1000.

Here we present not only the design of the instrument but also first data obtained during instrument commissioning at the 3.5-m Calar Alto telescope in December, 1993.

The Technical CCD Systems (TCCDS) consist of thermo-electrically cooled CCD detector heads together with the electronic hardware and software for the control of the CCD and readout of the data. Two different types of CCD heads equipped with a small and a large format CCD chip are used. The small format CCD systems will be used primarily for auto-guiding and field acquisition at the main foci of the VLT. The large format CCD systems are intended mainly for wavefront sensing applications. An overview of the primary modes of operation of the TCCDS and the corresponding fields and exposure conditions for these modes is given in Table 1. The term “Technical CCD Systems” is derived from the intended application in the VLT because due to the excellent CCD head parameters and the system performance a scientific application will be offered too.