I have recently turned my attention to some archival GALEX data and found it quite promising. What surprised me the most was the presence of galactic cirrus in the FUV (far ultraviolet) channel. Because I am unfamiliar with the "personality" of the telescope I almost mistook it for some kind of odd artifacting. As far as I know, this cirrus has never been presented in a GALEX image before, so I am happy to have found it there. If you are having a hard time seeing it, a brighter version is available here (6.7MB JPG).
Processing notes: Of greatest concern is the FUV-bright star (Nu Andromedae) in the lower left. There was no FUV data available; all came from a single, low duration NUV (near ultraviolet) exposure. The brightness of the star was interpolated based on nearby contextual clues from frames which did contain FUV information. It is definitely the brightest FUV source in the frame, and I think it was fair to "fake" it like this. From what I am able to gather, observations of bright FUV sources were avoided due to long-term issues with the detectors, so that is probably why there were never any exposures of this particular star.
Several areas are monochrome like this, mostly in the lower left corner and another near the southern tip of the galaxy. These filler data are very coarse and do not look good up close, but they had to suffice.
Many little annuli were removed, including a giant line of them emanating from Nu Andromedae. I tried to match the backgrounds of each frame as well as I could, but it's not by any means perfect. The NUV channel in particular was devilishly hard to match each disc-shaped frame against one another.
To make the local galactic cirrus more clearly visible, this image relies on complex (or at least, not-quite-simple) color channel assignments. It is similar to an orange-cyan (red-pseudogreen-blue) image, but some of the FUV data is shown a bit greener in the darker areas to bring out the cirrus. Visual aesthetic weighed heavily in the creation of this image, but bluer areas are more intense in FUV and redder areas are more intense in the NUV with the exception of monochrome areas which appear only cyan.
North is up.
Tags: Andromeda GALEX Nu Andromedae ultraviolet near ultraviolet far ultraviolet FUV NUV galaxy spiral mosaic astronomy M31 cirrus
The famous Helix Nebula in ultraviolet from the GALEX mission. There's a version out there that includes infrared data from Spitzer, relegating the GALEX data merely to the blue channel. I think it deserves an image of its own, all by itself. Of course, now I want to go dig around in Spitzer's archive...
Red: NUV (Near ultraviolet)
Green: Pseudo (R+G 50/50)
Blue: FUV (Far ultraviolet)
North is up.
Tags: planetary nebula GALEX ultraviolet FUV NUV
