Max-Planck-Institut für extraterrestrische Physik
Mirrors
Deutsche Version MPE HEG X-Ray Astronomy Wave ROSAT
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Mirrors
The WFC optics consist of a nested set of 3 Wolter-Schwarzschild
Type I mirrors, fabricated from aluminium and coated with gold
for maximum reflectance.
The mirrors provide a geometrical collecting area of
with a common focal length of 
.
The grazing incidence angles chosen (typically 
)
allow the collecting area to be optimised whilst retaining a wide
( 
radius) circular field of view and a high-energy
reflectivity cut-off at 
( 
).
The on-axis resolution is 2.3' HEW, degrading to 
HEW
at 
off-axis due to inherent optical aberrations.
The average resolution for the all-sky survey is 
HEW.
The mirror parameters are summarised in
Tab. 6.1.
| Mirror type | Wolter-Schwarzschild Type I |
| Mirror material | Ni plated Aluminium |
| Reflective coating | Au |
| Number of shells | 3 |
| Field of view |  diameter |
| Geometric area |  |
| Aperture diameter |  |
| Focal length |  |
| Focal plane scale factor |  |
| High energy cutoff (10% of peak) |  |
| Half energy width (on-axis) | 1.7' at  |
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