Large format digital camera (LFDC) systems are becoming more broadly available and regularly collect image data over large areas. Spectral and radiometric attributes of imagery from LFDC systems make this type of image data appropriate for semi-automated change detection. However, achieving accurate spatial co-registration between multitemporal image sets is necessary for semi-automated change ...

Multiwavelength observations of polars are essential for developing the big picture of these systems, particularly to gain understanding of the relevant accretion-induced heating and cooling processes. Eclipsing polars are prime targets for such studies since different radiation processes can be disentangled by observations with high-time resolution. We present a preliminary combined analysis o...

The central engines of disc-accreting stellar-mass black holes appear to be scaled down versions of the supermassive black holes that power active galactic nuclei. However, if the physics of accretion is universal, it should also be possible to extend this scaling to other types of accreting systems, irrespective of accretor mass, size, or type. We examine new observations, obtained with Kepler...

We present light curves of SDSS J0926+3624, the first eclipsing AM CVn star, observed with the high-speed CCD camera ULTRACAM on the WHT. We find unusually that the accreting white dwarf is only partially eclipsed by its companion. Apart from this, the system shows the classic eclipse morphology displayed by eclipsing dwarf novae, namely the eclipse of a white dwarf and accretion disc followed ...

We have discovered a pulsating DA white dwarf at the lower end of the temperature range 45 000–30 000 K where a few helium atmosphere white dwarfs are known. There are now three such pulsators known, suggesting that a new class of theoretically predicted pulsating white dwarf stars exists. We name them the hot DAV stars. From high-speed photometric observations with the ULTRACAM photometer on t...

A test area north of Philadelphia was flown with Vexcel Imaging UltraCamD, UltraCamX and Z/I Imaging DMC digital frame cameras as well as with the 3D-CCD-line scanner camera Leica ADS40 and the analogue RC30. The frame images have 60% overlap in both directions. The object resolution is approximately the same with ~ 5cm ground sampling distance (GSD). 42 well defined control and check points ar...