An all-sky optical catalogue of radio / X-ray sources
  We present an all-sky catalogue that aligns and overlays the ROSAT HRI, RASS, PSPC and WGA X-ray catalogues and the NVSS, FIRST and SUMSS radio catalogues onto the optical APM and USNO-A catalogues. Objects presented are those APM/USNO-A optical objects which are calculated with >= 40% confidence to be associated with radio/X-ray detections, or which are identified as known QSOs, AGN or BL Lacs, totalling 501,761 objects in all, including 48,285 QSOs and 21,498 double radio lobe detections. For each radio/X-ray associated optical object we display the calculated percentage probabilities of its being a QSO, galaxy, star, or erroneous radio/X-ray association, plus any identification from the literature. The catalogue includes 86,009 objects which were not previously identified and which we list as being 40% to >99% likely to be a QSO. As a byproduct of the construction of this catalogue, we are able to list comprehensive ROSAT field shifts as determined by our whole-sky likelihood algorithm, and also plate-by-plate photometric recalibration of the complete APM and USNO-A2.0 optical catalogues, significantly improving accuracy for objects of >15 mag. The catalogue is available wholly and in subsets at http://quasars.org/qorg-data.htm 
E. Flesch and M. J. Hardcastle