This document updates and extends the photographic catalog of selected planetary size comparisons. It utilizes photographs taken by NASA spacecraft to illustrate size comparisons of planets and moons of the solar system. Global views are depicted at the same scale, within each comparison, allowing size relationships to be studied visually.

In this paper we report the results of simultaneous observations, using rapid continuous differential photometry, of the δ Scuti star 63 Her and of a normal main sequence F2V star, HD 155543. These observations, which lasted three weeks, in May-June 1987, were performed at the 1.5 m telescopes of the "Observatorio del Teide", in Tenerife (Spain)

The results of optical spectroscopy and photometry of V404Cyg, the optical counterpart of the recently discovered X-ray transient GS2023 + 338, are presented. Optical spectra were obtained at the Roque de los Muchachos Observatory with the 2.5-mm Isaac Newton Telescope. The overall optical light curve was found to be similar to that of an earlier

SE COMIENZA CON UNA DESCRIPCION DE LOS PROBLEMAS MAS IMPORTANTES QUE APARECEN EN EL ESTUDIO DE LAS POBLACIONES ESTELARES, ASI COMO DE LOS METODOS EMPLEADOS HASTA AHORA PARA SU TRATAMIENTO. A PARTIR DE ESTA INTRODUCCION SE MUESTRAN LOS MODELOS DESARROLLADOS EN ESTE TRABAJO, DETALLANDO TANTO LOS METODOS MATEMATICOS COMO LAS IDEAS FISICAS SOBRE LAS

Simultaneous UBVRI photopolarimetric observations of the highly variable BL Lac object OJ 287 have been obtained on six nights. The polarization and position angle, as well as their wavelength dependence, have been found to be variable from night to night and also on a timescale of a few hours. During the first three consecutive nights, a clear

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