We present the result of a study on the expansion properties and internal kinematics of round/elliptical planetary nebulae of the Milky Way disk, the halo, and of the globular cluster M 15. The purpose of this study is to considerably enlarge the small sample of nebulae with precisely determined expansion properties (Schönberner et al. \cite{SJSPCA

Context. K-means is a clustering algorithm that has been used to classify large datasets in astronomical databases. It is an unsupervised method, able to cope very different types of problems. Aims: We check whether a variant of the algorithm called single pass k-means can be used as a fast alternative to the traditional k-means. Methods: The

Telescopes on the North Atlantic Islands of La Palma and Tenerife, in the Canary Islands Archipelago have recorded optical extinction for approximately 30 years whilst making routine astronomical observations. In La Palma, these measurements come from stellar measurements, while in Tenerife, these measurements come from solar observations. We have

Quasars are considered to be the most luminous subclass among Active Galactic Nuclei. Although they appear to be distributed everywhere in the Universe, only a small fraction of them happen to be part of a fortuitous alignment with a galaxy or a galaxy cluster that lies along the line-of-sight, which results in multiple images of the background

We present a study of the spatial variation of forecast conditions at La Palma, Canary Islands. Previsions are obtained with the Weather Research and Forecasting (WRF) model in combination with the Trinquet-Vernin (TV) model, which allows us to compute the optical turbulence from the vertical gradient of the temperature and the wind velocity. The

We show that the morphology of the initial monolayers of InP on Al0.48In0.52As grown by metalorganic vapor-phase epitaxy does not follow the expected layer-by-layer growth mode of lattice-matched systems, but instead develops a number of low-dimensional structures, e.g., quantum dots and wires. We discuss how the macroscopically strain-free