This is in semi-false Sloan colors, with i' -> red, r' -> green, g' -> blue. This gives a wider spectral range with no gaps, and maps Ha regions to green - just as with the "Hubble Palette" used for narrowband imaging.
The colors calibrated by custom code based on UCAC4 field stars with AMASS Sloan photometry. The color calibration was
deterministic, with Photoshop CS6 applying only levels. The result for this galaxy helps distinguish the green Ha regions from the old, orange star clusters. Two distant galaxies in the upper left have a similar orange color.
|Imaging Optics||Celestron EdgeHD 11 with reducer at f/7|
|Guiding Software||MetaGuide with dithering from SGP|
|Guiding Mode||Off-axis guiding with Hutech OAG5|
|Imaging Camera||Atik 383L+|
|Focus||SGP and RoboFocus on the primary focuser - no mirror locks used|
|Exposure Time||3x20x1m Exposures kept short to avoid saturating|
|Image Scale||0.57" per pixel|
|Raw FWHM||Down to 2.0" in subs|
|Image Processing||Calibration and stack in custom software, only levels in Photoshop CS6 - no other processing|
|Image Processing - Other||Colors calibrated with Sloan magnitudes using UCAC4 field stars and custom code|
|Other Software||PECTool, TheSkyX Pro for best guidestar selection with field of view indicator (FOVI)|
|Other Hardware||Pyxis OAG Rotator for best guidestar, Telegizmos 365 cover, Long usb cable to outside setup|
|Date||July 20-1, 2015|
|Filter||Astrodon Sloan i', r', g'|
Close up of core at double resolution (0.28"/pixel). Note the multiple elements in the central region, with color distinguishing bright Ha regions from bright stellar regions.
Compare with Gemini image showing double nucleus
The star formation is evident in the green Ha regions, while the original nucleus
shows as the bright orange feature near the center - corresponding to a mass of 2 million suns. Unseen is the newly discovered intruding mass of 16 million suns.