This publication utilizes photographs taken by NASA spacecraft, and cartographic products based on these photos, to illustrate size comparisons of the planets and moons of the solar system. It depicts both global views and prominent geographical features at the same scale, allowing size relationships to be studied visually.

The characteristics of the chromospheres of late-type dwarf stars were studied using the CoudeEchelle Spectrograph (CES) at ESO and the IUE. The study focused on the h and k Mg II lines of F and G dwarfs. The stability of the IUE spectra permitted calculations of averaged absorption features and the subtraction of the Mg II lines to leave intrinsic

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The spectrum corresponding to the emission of radiation from a dust distribution dominated by the dynamical action of the Poynting Robertson Effect is discussed and a model is applied to the dust surrounding Vega. It is found that a dust cloud extending from 41 to 177 AU match the 25, 60 and 100 micron measurements from IRAS. The 193 micron data

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