NGC 1491 | SH2-206 – an emission nebula in Perseus

NGC 1491 (also designated Sharpless SH2-206) is a bright emission nebula and HII region, located on the edge of a vast cloud region of neutral gas, about 10,700 light-years away in the Perseus arm of our Milky Way galaxy.  The stellar wind from the O5V 11.2 magnitude star (BD +50 886) at its centre is forming a blister in the gas clouds immediately surrounding it while also eroding the gas clouds.

HII regions are well known for being places where new stars are born, and are created when ultraviolet radiation from hot stars ionizes the surrounding gas, causing it to glow in visible and infrared light.  This is a faint nebula and required over nine hours of integration time at each emission line to reveal the detail across the entire nebula.

MaxIm DL v6 was used to calibrate, align and stack the sub exposures.  PixInsight v1.8 DBE (Dynamic Background Extraction) was used in the absence of suitable flat frames to remove sky background noise and gradients.  Photoshop CC 2014 layers and layer mask processing techniques were used for colour enhancement and to tease out the detail – Levels, Curves, Reduce Noise, Selective Color, HDR toning, Smart Sharpen and Unsharp Mask in predominant use.

Right ascension: 04h 03m 14s | Declination: +51° 18' 58" | Distance: 10,700 Light Years
Field of view: 54 x 37 arcmin

Camera: SBIG ST-10XME
Telescope: APM 152-1200ED F/6.2 with Riccardi x0.75 Reducer
Guiding: Off-axis with Lodestar guider
Filters: Astrodon Ha (3nm), OIII (3nm), SII (3nm)
Exposures: Ha 28 x 20 min, OIII 27 x 20 min, SII 29 x 20 min
Total exposure: 28 hours
Image composition: False Colour Hubble Palette (SII, Ha, OIII mapped to RGB)
Scale: 1.49 arcsec/pixel
Image acquired: 23rd November 2014 – 6th February 2015

Image capture with MaxIm DL, FocusMax, ACP; Image processed with MaxIm DL; PixInsight; Photoshop CC 2014