We focus on short--period eclipsing binaries that belong to a class of Cataclysmic Variables (CVs). They are known as polars and intermediate polars, closely resembling their prototype AM Herculis. These binaries consist of a red dwarf and a strongly
magnetic white dwarf, having orbital periods of only a few hours. Monitoring eclipses of these typically faint sources demands high-time resolution photometry. We describe the very recent results obtained for two CVs, HU Aqr and DQ Her, which were observed with the Optical Pulsar Timing Analyzer (OPTIMA). The new observations of HU Aqr confirm that the O--C (Observed minus Calculated) diagrams exhibit variations known for this binary which can be explained by a single, massive Jupiter--like planet, possibly accompanied by a very distant companion.
The linear polarisation of the Crab pulsar and its close environment was derived from observations with the high-speed photo-polarimeter OPTIMA at the 2.56-m Nordic Optical Telescope in the optical spectral range (400 - 750 nm). Time resolution as sh
ort as 11 microseconds, which corresponds to a phase interval of 1/3000 of the pulsar rotation, and high statistics allow the derivation of polarisation details never achieved before. The degree of optical polarisation and the position angle correlate in surprising details with the light curves at optical wavelengths and at radio frequencies of 610 and 1400 MHz. Our observations show that there exists a subtle connection between presumed non-coherent (optical) and coherent (radio) emissions. This finding supports previously detected correlations between the optical intensity of the Crab and the occurrence of giant radio pulses. Interpretation of our observations require more elaborate theoretical models than those currently available in the literature.
