IAUC 5079 available at Central Bureau for Astronomical Telegrams.

IAUC 5078 available at Central Bureau for Astronomical Telegrams.

The effect of a spiral-like perturbation in the orbits of an axisymmetric galactic potential is studied using surfaces of section. It is found that the perturbation induces stochasticity and diffusion of orbits in phase space.

An aspect of the missing mass problem in galaxies, not easy to address, is whether the dynamical mass distribution is spherical or greatly flattened, following the light. Rotation curves of spirals out of the plane of the disk cannot, by definition, be measured. A way around this problem might be to use satellite galaxies orbiting within a few

From high-resolution CCD images of granulation obtained at the Swedish Solar Tower of the Observatorio del Roque de los Muchachos at different positions on the solar disk, mean bi-dimensional spatial power spectra have been obtained at each position and restored following the method proposed by Rodriguez Hidalgo et al. (1990). The variation with

High-resolution CCD images are presented of a sample of spiral galaxies, in infrared photometric bands, obtained at the Cassegrain focus of the 1 m Jacobus Kapteyn Telescope, La Palma. A decisive advantage of the linearity in these images is that a reliable separation of the light from bulge and disk can be effected. Possible applications of the