Detections of transiting planets from the upcoming PLATO mission are expected to face significant contamination from contaminating eclipsing binaries, resulting in false positives. To counter this, a ground-based programme to acquire time-critical photometry is pursued. Its principal aim is to obtain time-series observations of the planet candidate

In this study, we look specifically at binary white dwarfs where the companion is a main sequence star. In particular, we look at very hot white dwarfs, many of which demonstrate the "hydrogen problem" in which modeling of their hydrogen absorption features, and optical features in general, do not appear to give accurate temperatures. The two

We present here binary modeling for the close binary central star of the planetary nebula Hf 2-2. While binary models for 26 close binary star systems within a planetary nebula exist, this number is far too low to perform a significant statistical analysis. In order to work towards increasing this number, and thus improving the statistical results

We report on follow-up studies of transient events and objects, which have been conducted in recent years using ground-based optical observations. BVRI photometry has been performed with small and medium-sized telescopes located in Europe and North America. The purpose of these studies, which are mainly focused on objects of unknown nature, is to

Understanding telescope pointing (i.e. line of sight) is important for observing the cosmic microwave background (CMB) and astronomical objects. The Moon is a candidate astronomical source for pointing calibration. Although the visible size of the Moon (30') is larger than that of the planets, we can frequently observe the Moon once a month with a

The origin of obscuration in active galactic nuclei (AGNs) is still an open debate. In particular, it is unclear what drives the relative contributions to the line-of-sight column densities from galaxy-scale and torus-linked obscuration. The latter source is expected to play a significant role in Unification Models, while the former is thought to