lines, albeit at modest spatial resolutions. Higher spatial resolution FUV images of selected regions in the Cygnus Loop are available from the Ultraviolet Imaging Telescope (UIT). Danforth et al. (2000) show comparisons of UIT images to both X-ray and optical images, indicating all wavelengths are patchy and show relative spatial variations. Even though the UIT bandpass did not isolate individual emission lines, spatial variations of the FUV emission are clearly present. Some of the spectroscopic positions observed in the Cygnus Loop and Vela SNRs also correspond to very faint optical filaments and yet the UV emission is bright (Sankrit et al. 2001; Blair et al. 2002; Sankrit & Blair 2002; Raymond et al. 2003).

A serendipitous $\fuse$ observation of a SNR in the SMC H II region NGC 346 (N66) has provided another important example of potential observational bias (Danforth et al. 2003). With the $\fuse$ MDRS aperture placed on a star in the NGC 346 star cluster, strong O VI and C III $\lambda$977 emission lines were detected in the LWRS aperture a couple of arcminutes away. Reconstructing the LWRS aperture location showed that it was projected onto the limb of a known radio SNR 0057-7226 (Ye, Turtle, & 