Optical Ghosts in NIC 1 Polarizers
DIAGNOSTIC:
Data taken with the NICMOS Polarimetry filters exhibit
optical ghost images (in addition to the electronic ghosts known as
the "Mr. Staypuft" effect). The optical
ghosts are most evident for the short wavelength polarimeters
in NIC1. As shown in the images above, the ghosts have different
positions with respect to the principal axes of transmission.
For POL0S, a ghost image appears at position (-10,+35) pixels
relative to the target source, and a second one at (-16,+70) pixels.
It is possible that for a brighter object more ghosts would appear along
the same direction. For POL120S, no ghosts have been found.
As for POL240S, ghosts are present at (+10,+54)
and (+18,+80) pixels from the source position, with possibly more
for brighter targets.
The other (non-polarizing) NICMOS filters show only very low-level,
highly defocused ghost images which will only become apparent in
PSF-subtracted images (see the
analysis by Krist et al. 1998).
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