A two-dimensional velocity map in H-alpha of the inner 4 arc min zone of the Scd starburst galaxy NGC 6946 has been obtained using the TAURUS interferometric spectrometer on the 2.5 m Isaac Newton Telescope. The major axis rotation curve is a clean kinematic superposition of a central 1 kpc sphere with solid body rotation and a disk with density

For determining the adiabatic stability of a uniform vertical field in an arbitrary stratification it is sufficient to consider the limit of infinitesimal horizontal wavelength. It is shown how the behavior of the instability can be estimated qualitatively from the dependence of the equipartition field strength on depth. Modes are calculated

We report the first results obtained from a continuing programme of spectrophotometric monitoring of high luminosity active galactic nuclei (AGN). Analysis shows that significant emission line variations take place in high luminosity, high redshift objects. These variations occur on time-scales much shorter than those expected from photo-ionization

The 2.5-m Isaac Newton telescope has been used in a spectrophotometric monitoring program of high-luminosity AGN. The data acquisition and analysis techniques are first discussed. A comparison of the L-alpha, C IV, and C III profiles reveals that the profiles of different lines in a single object are not always the same as each other. An analysis

From H-alpha CCD observations taken with the 4.2 m William Herschel Telescope a catalog of 394 HII regions of the spiral NGC 3992 has been compiled. The distribution of diameters and the luminosity function for the arm and the interarm HII regions has been studied.

CCD photometry and MERLIN observations of M87 (Virgo A) have been used to study the variations of the radio to optical spectral index along the jet. In general, the radio spectrum is flatter than the optical one and both become steeper with distance from the nucleus. The optical fluxes of the bright knots lie at or below the extrapolation of the