Optical Ghosts in NIC 1 Polarizers
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 inPSF-subtracted images (see the analysis by Krist et al. 1998).