I have wide-ranging interests in many areas of astrophysics ranging from extrasolar planets to black hole accretion in galaxies to alternative gravity theories. My main expertise is in the interpretation of astrophysical observations, in particular developing novel data analysis and astro-tomography methods that extend the reach and resolution of observational data.

In the 1980's I worked mainly on accretion in compact binary systems, developing eclipse mapping and doppler tomography methods to make micro-arcsecond maps of the temperature profiles and emission-line distributions on the faces of the accretion disks in cataclysmic variables. For this I developed the optimal extraction algorithm for CCD spectroscopy, and maximum entropy reconstruction methods to convert the observed eclipse lightcurves and orbital phase variations of the emission-line profiles into accretion disk maps. (I developed similar methods to map x-ray coronae of rotating stars, and to make albedo maps of Pluto and Charon from mutual event lightcurves.)

In the 1990's I worked also on echo mapping of accretion flows into the supermassive black holes of active galactic nuclei, using light travel time delays to resolve structures 1-100 light days from the black hole, including the accretion disk and the broad emission-line regions. I adapted the maximum entropy methods to recover delay dsitributions and 2-dimensional velocity-delay maps of various emission-line regions, revealing their stratified ionisation structure and some aspects of the gas kinematics (virial flows) from which black hole masses and accretion rates are be measured.