Redshift observations of 30 clusters in the direction of the Sextans-Leo supercluster candidate are reported. The observations are part of a program which involves mapping the universe's large-scale structure, and include North Galactic Cap Abell clusters, Abell clusters that have only been partially observed, and unmeasured poor Zwicky clusters

The site of the solar spectrometer of the International Research on the Interior of the Sun (IRIS) network, installed in December 1989 in the Teide Observatory (Izana, Tenerife) is described together with the instrumental facilities of the Teide Observatory. The IRIS instrument is housed at the Solar Oscillation Laboratory of the observatory, which

The present study of the local insterstellar medium toward the center of Loop I analyzes optical and UV spectra of nearby stars within the l = 310-330 deg, b = 15-25 deg area. The analysis of the UV spectra reveals a sudden gas-column density increase as a function of distance from 10 to the 18th to 10 to the 20th/sq cm, suggesting the presence of

The technological choices selected for the need of the International Research on the Interior of the Sun (IRIS) network are examined. Special attention is given principles of electronic measurements by the IRIS instrument, the instrument's critical components and specific requirements, and calculations of theoretical sensitivity of the IRIS

A general panorama of SS Cygni is presented. The paper first describes the CV cataclysmic variables and the current theories which attempt to describe their physical behavior. The up-to-data observational properties of SS Cygni are examined together with an explanation of their nature within the framework of existing theories.

The question of which estimator of the two-point correlation function has the smallest sampling error is discussed. An expression is given for this smallest sampling error in terms of the correlation functions, although it is found to be of rather limited use. A more useful approach is considered, in which the sampling error is shown to be made up