
17.2.
Signal-to-Noise Ratio 433
2=1 |im, F = 30, and pixel size A = 15 jim, then there are two pixels spanning
length AF. For this correctly sampled wavelength, the value of
Z
does not depend
on the precise position of the peak of the PSF on the pixel array. Whether this
peak is centered on one pixel or is at a comer of
a
pixel is of
no
consequence. If,
however, a PSF of a shorter wavelength is used, then the PSF is undersampled
(XF < 2A) and the position of the PSF on the array does affect the value of
Z.
Not
surprisingly, Z is largest for an undersampled wavelength when the peak of the
PSF is centered on one pixel.
17.2.
SIGNAL-TO-NOISE RATI ...