Three clusters were selected which have low to intermediate X-ray luminosity and show at the same time a very irregular structure in the RASS: A901, A1437, and A3570 (the RASS images will be published by Böhringer et al.). For this analysis X-ray and optical observations were conducted. The X-ray observations were carried out with the ROSAT/HRI (Trümper 1983) and analysed with EXSAS. The optical observations consist of spectra taken with MEFOS (Felenbok et al. 1997) at the ESO 3.6 m telescope. The analysis of the spectra was carried out with Figaro. The spectra determine the distance of the cluster in the case of A901 and for A3570 a velocity distribution. Details of the optical and X-ray observations are listed in Table 1.
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