We have developed a local-detect algorithm using the Mexican-Hat function as a lter to detect X-ray sources in the 3-dimensional space-time domain. Our method takes advantage of the limited spatial and frequency extents of the Mexican-Hat function to allow the correlation to be done in pieces small enough to be handled on standard workstations. We apply this algorithm to ROSAT PSPC data of the ...

By using images taken with WFCAM on UKIRT and SofI on the NTT and combining them with 2MASS we have measured proper motions for 126 L and T dwarfs in the dwarf archive. Two of these L dwarfs appear to have M dwarf common proper motion companions, and 2 also appear to be high velocity dwarfs, indicating possible membership of the thick disc. We have also compared the motion of these 126 objects ...

Hipparcos observations of open clusters provide mean cluster parallax determinations with an unprecedented accuracy. Possible biases in the Hipparcos parallaxes exhibited by other authors has been analysed and proven not to exist. A comparison of observed (V; B ? V) diagrams of the Pleiades and Praesepe with theoretical isochrones has been performed. It does not exhibit disagreement with Hippar...