Optical and radio data from the 1989 minimum are analyzed to examine the implications of the light curves for the spectrum. The optical spectrum increases between maximum and minimum with a sharp peak in the continuum, and a normal shape is noted at the minimum. The data are suggestive of a self-absorbed synchrotron component in the accretion disk

A technique for obtaining an ideal two-mirror coude system with no instrumental polarization is described. A half-wave plate positioned between the two mirrors with the proper orientation produces the desired effect. The level of spurious polarization is limited by the characteristics of the retarder and the similarity of the mirrors. The telescope

Markarian 50 is analyzed using V and I CCD frames and IPCS and CCD spectra, obtained in June 1985, covering the range 3200-10,000 A. It is inferred from the surface brightness profiles derived from the images that this is an early-type, elliptical, or S0 galaxy, which is supported by the spectral analysis of the stellar population. After

This book is a collection of papers by four internationally known speakers who explore some key areas in solar physics. O. von der Lühe discusses new techniques that are being developed for observing the sun at high spatial resolution and which have played a key role in most of the recent discoveries about the Sun. Egidio Landi Degl'Innocenti

An analysis of 50 optical spectra of the interstellar methylidyne ion in the direction of HD26676 and HD149038 derived very similar interstellar isotopic ratios for the two lines-of-sight. A lack of a Galactic gradient in isotopic ratios is noted which is consistent with the location in the solar vicinity of the gas in front of HD149038. The

Irradiance measurements from the IPHIR instrument flown on the Phobos 2 mission to Mars are used to derive phase differences and gains between broadband relative irradiance signals and full-disk velocity variations for l = 0, 1, and 2 mode with order ranging from 12 to 32. These data are compared with contemporaneous measurements of photospheric