This is a somewhat different view of the Running Man Nebula (NGC1977) encompassing wavelengths from Infrared to Ultraviolet using data from the Sloan Digital Sky Survey (SDSS) project.
Quick summary of hardware: SDSS uses a 2.5m F/5 modified Ritchey-Chrétien telescope with an imaging camera made up of 30 CCD chips, with 5 different filters r, i, u, z, g (
https://www.sdss.org/).
Even though the SDSS has a large field of view (at least for a 2.5m scope!), I had to stitch into a mosaic 8 panels for each of the 5 available filters.
The color image has the following channel assignation:
-R channel -> Infrared (“z” and “i” filters)
-G channel -> Visible spectrum (“r” and “g” filters)
-B channel -> Ultraviolet (“u” filter)
This “zi-rg-u” palette extends our human eye perception in both directions since long wavelengths are assigned to the Red channel, while the UV ones are assigned to the Blue channel. What we typically perceive with our eyes is compressed into the Green channel between the IR and the UV.
Image processing: SDSS data is great, however, there were a lot of small artifacts (some are still there in the final image) that had to be reduced or smoothed. Apart from this (long and tedious) work I used some noise reduction and contrast enhancement in PixInsight. The colors just pop out by themselves using the “zi-rg-u” palette, but I increased the saturation for purely aesthetic purposes.
SDSS citations and acknowledgments for the data:
https://www.sdss.org/collaboration/citing-sdss/
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