EPIC X-ray Straylight Calibration - Crab Nebula offset

CAL We measure the amount and structure of stray Xray light focussedinto the EPIC field of view as a result of bright offaxis sourcesscattering via single mirror reflections. The adoption of Crab at arange of offaxis angles utilises the wellknown source spectrum to obtainthe fastest means of obtaining the required S:N ratio. The observationguarantees that the scattered light is above diffuse background levels