Shadowing Studies in the Moderate (CCD) Resolution Era

Shadowing experiment in the direction of neutral hydrogen clouds have been an important tool in the study of the diffuse X-ray background since the launch of ROSAT in 1991. In the current era of CCD detectors, shadowing experiments have evolved to 'contrast' experiments, where on-cloud and off-cloud spectra are compared to separate foreground and background components. The separation, combined with the improved resolution of the CCD detectors, allows a first order spectral analysis of the individual diffuse X-ray background components. In this paper we review the main shadowing experiment performed with Chandra, XMM-Newton, and Suzaku, and we discuss the results to extract some global properties of the diffuse emission.