IC 5146 - Cocoon Nebula
Acquisition and processing
This images was taken over 2 nights, September 6th and 7th 2021 on a new moon night. I used the TS Photoline 130/910 with my standard reducer/flattener to f5.5. I went for RGB in combination with luminance and H-alpha. The last two I used to combine them in PixInsight to create an own luminance channel (0.15*Ha+0.85*L). This channel was than integrated in the RGB with LRGBCombination. In total 10.93 hrs of integration, which was done in Astro Pixel Processor.
Subframes: R 23x120" and 24x180", G 23x120" and 21x180", B 26x120" and 17x180", L 85x120" and 3x180", Ha 46x180"
Calibration frames: 20 Darks, 30 Bias, 20 Flats and 20 Darkflats (for Ha)
Camera settings: Gain 139, Offset 21, Temp. -20°C for Ha and Gain 75, Offset 10 for LRGB
IC 5146, Caldwell 19 and also named the Cocoon Nebula is a reflection/emission nebula and Caldwell object in the constellation Cygnus. The NGC description refers to IC 5146 as a cluster of 9.5 mag stars involved in a bright and dark nebula. It is located near the naked-eye star Pi Cygni, the open cluster NGC 7209 in Lacerta, and the bright open cluster M39. The cluster is about 4,000 ly away, and the central star that lights it formed about 100,000 years ago. The nebula is about 12 arcmins across, which is equivalent to a span of 15 light years.
When viewing IC 5146, dark nebula Barnard 168 (B168) is an inseparable part of the experience, forming a dark lane that surrounds the cluster and projects westward forming the appearance of a trail behind the Cocoon.