SIMBAD references

Based on the experience made with ROSAT observations we discuss the practical constraints on the analysis of dust scattered haloes around X-ray sources. After a brief review of the theoretical framework and the input parameters for the study of X-ray haloes relevant for our purposes, we describe the instrumental behaviour of the ROSAT X-ray telescope in combination with the Position Sensitive Proportional Counter (PSPC) in view of its relevance to the measurement of X-ray haloes. Then, the impact of various parameters on the intensity profile of X-ray haloes are studied.