ASCA XRT Performance:

ASCA XRT effective area (one telescope) for different off-axis angle (theta) and azimuthal angle (phi).

Off-axis angular dependence of the XRT effective area (one telecope) for two energies and two azimuthal angles.

Point spread function (PSF) of ASCA XRT for four different off-axis angles.
Approximate field of view is shown for GIS (circle) and SIS (square).