Figure 1: The deviation in RA and Dec between X-ray positions (LECS, MECS1, MECS2, MECS3) and optical positions. The short-dashed circle has a radius of 30 arcsec. Note that coordinates differences have been computed subtracting the X-ray value from the optical one and that RA differences are corrected by the factor cos(Dec). "Delta RA" values represent therefore the true separation in the sky.