A total of 85 UBVRI observations of BL Lac objects is presented. For most of them, an average continuum can be traced by means of well-defined color indices. These continua are always well reproduced by power laws, strongly supporting the hypothesis of a synchrotron origin of the radiation output, as well as the conclusion that there is no dust in

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Infrared observations of symbiotic stars, together with simultaneous optical and ultraviolet observations are demonstrated to be a powerful tool for the understanding of their nature.

Visual, scaled comparisons are made among prominent volcanic, tectonic, crater and impact basin features photographed on various planets and moons in the solar system. The volcanic formation Olympus Mons, on Mars, is 27 km tall, while Io volcanic plumes reach 200-300 km altitude. Valles Marineris, a tectonic fault on Mars, is several thousand