One of the "problems" with imaging
Eta Carinae in SII luminance is that the longer wavelength of the SII emission can cut through the dark nebulae in the region and reduce contrast in these areas.
By merging separate HaRGB and OIIIRGB images with the SIIRGB image, the dark regions are preserved.
Large image here.
http://members.iinet.net.au/~sjastro...I_SII_rgb.html
Comparison SII luminance image here.
http://members.iinet.net.au/~sjastro/etaSIIc.html
Clear skies
Steven