Max-Planck-Institut für extraterrestrische Physik
F.8 Correction for XRT Field Distortion
Deutsche Version MPE HEG X-Ray Astronomy Wave ROSAT
Next: F.9 Quantitative Illustration Up: PSPC Calibration Files for Previous: F.7 Window Correction
F.8 Correction for XRT Field Distortion
The plate scale varies slightly across the FOV.
This is caused by the almost flat detector (PSPC as well as HRI)
while the focal surface of the XRT is curved.
The resulting distortion effect --shift to larger off-axis angles--
has been simulated using ray-tracing programs.
It depends on the apparent off-axis distance d,
the apparent off-axis angle 
and
the off-axis distance dependent shift 
shown in
Fig. F.14.
The correction results in the final detector coordinates
and 
.
Parameters:
-
- off-axis shift
-
- apparent off-axis angle
-
, 
- detector coordinates (electronic position correction and window correction applied)
-
, 
- on-axis position, determines the detector center
-
, 
- detector coordinates (electronic position correction, window correction and correction for XRT field distortion applied)
d] apparent off-axis distance
If you have problems/suggestions please send mail to xray-info @ mpe . mpg . de