This image is a narrowband presentation of hydrogen, and oxygen emission lines, mapped to red and blue respectively, with the green channel synthesized as Ha x OIII. Stars colours were captured with shorter exposures using RGB filters.
I like this combination as it shows a nice rainbow of colours where both OIII and Ha are present in various quantities.
**Image:**
* 31x 900s 6nm H-alpha + 10 flat + 50x dark + 120x bias
* 30x 900s 6nm OIII + 15 flat + 50x dark + 120x bias
* 18x 40s + 15x 20s Red + 10 flat + 50x dark + 120x bias
* 18x 40s + 16x 20s Green + 10 flat + 50x dark + 120x bias
* 19x 40s + 19x 20s Blue + 10 flat + 50x dark + 120x bias
Total exposure 16 hours 8 minutes.
**Hardware:**
* Skywatcher Black Diamond ED120
* SkyWatcher EQ8 Pro Mount
* QSI 683-ws Camera @ -15°C
* Astronomik 6nm Ha, 12nm SII, 12nm OIII, typ 2c RGB filters
* Starlight Xpress Lodestar X2 Autoguider
* Innovations Foresight On Axis Guider
* Starlight Instruments Focus Boss II
**Location:**
* Orange zone in Brisbane, Australia. (Bortle 7)
* Imaged over 6 nights, high temperatures & humidity, new moon.
**Software:**
* Planning & camera alignment with Aladin 9
* Captured with AstroArt 6
* Guiding with PHD2 + PHD_Dither
* FocusLock live focusing
* CCDInspector: Image analysis & rejection
* CCDStack 2+: Calibrate, align, stack, combine RGB.
* Photoshop CC: Reduce noise, high pass filter, gradient removal, levels, curves, color map, saturation.
