Admiring the Universe - a fine-art photographer based in Perthshire, Scotland, with interests in landscape, nature and astrophotography

Sharpless Sh2-155 ("The Cave") Nebula

Sharpless Sh2-155 ("The Cave") Nebula
Sh2-155 s a diffuse nebula in the constellation Cepheus, within a larger nebula complex containing emission, reflection, and dark nebulosity. At an estimated distance of 725 parsecs (2400 ly), Sh2-155 is an ionized H II region with ongoing star formation activity.

SkyWatcher 80ED, IDAS NBZ dual-narrowband filter
112 * 300s lights
128 darks, flats and bias calibration frames

At 9hr20 the OIII signal was still very weak and tricky to process, requiring a lot of noise-reduction trickery. I'll definitely have to return to this target again.

The colour palette is particularly weird. Normal HOO tends to be strident reds and blues; HaHOO makes for paler yellow-gold and cyan colours. After a bit of playing around, this formula of my own gives excellent cold blue-green tonality instead.

// R:
OIII^2 + Ha/2

// G:

// B:
Ha + 0.5*OIII^2


Camera: ISO:
Focal Length: mm (mm-e) Aperture: f/
Shutter Speed: s


GPS location: ,