Caldwell 19 | Sh2-125
IC 5146, Cocoon Nebula
47’ x 31’ | 0.3”/px | 9359 × 6178 px | full resolution
Cygnus
RA 21h 53m Dec +47° 15’ | 0°
Caldwell 19, also known as Sh 2-125, IC 5146 and the Cocoon Nebula, is a reflection/emission nebula 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. 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. IC 5146 is a stellar nursery where star-formation is ongoing. Observations by both the Spitzer Space Telescope and the Chandra X-ray Observatory have collectively identified hundreds of young stellar objects. Young stars are seen in both the emission nebula, where gas has been ionized by massive young stars, and in the infrared-dark molecular cloud that forms the "tail".
source: Wikipedia
Data Acquisition
Data was collected over 8 nights during late August and September 2025, using a 14” reflector telescope with full-frame camera at the remote observatory in Spain. Data was gathered using standard LRGB filters. A total of approximately 18 hours of data was finally combined to create the final image.
Location Remote hosting facility IC Astronomy in Oria, Spain (37°N 2°W)
Sessions
Frames
Equipment
Telescope
Mount
Camera
Filters
Guiding
Accessoires
Software
Planewave CDK14 (2563mm @ f/7.2), Optec Gemini Rotating focuser
10Micron GM2000HPS, custom pier
Moravian C3-61000 Pro (full frame), cooled to -10 ºC
Chroma 2” LRGB unmounted, Moravian filterwheel L, 7-position
Unguided
Compulab Tensor I-22, Dragonfly, Pegasus Ultimate Powerbox v2
Voyager Advanced, Viking, Mountwizzard4, Astroplanner, PixInsight 1.9.3
Processing
All processing was done in Pixsinsight unless stated otherwise. Default features were enhanced using scripts and tools from RC-Astro, SetiAstro, GraXpert, CosmicPhotons and others. Images were calibrated using 50 Darks, 50 Flats, and 50 Flat-Darks, registered and integrated using WeightedBatchPreProcessing (WBPP). The processing workflow diagram below outlines the steps taken to create the final image.
Most of the processing was pretty standard, but a few additional tweaks were added. I have been experimenting a bit with stricter rejection criteria for images. The impression is that specifically the bright stars with the diffraction spikes come out a bit more symmetrical. What I noticed is that for some stars this can cause a bit of noise in the final stars image, so an extra noise removal step in the processing of the stars was added.
The final image looked a bit too bright in the pinks for my taste, so saturation on the pinks was reduced with Colorsaturation. Also, the small blueish nebula next to the Cocoon nebula was a bit greyish. Just increasing the blues would emphasise the two very bright blue stars in the image too much, so a simple GAME mask was used to protect the image while blue was selectively increased for the nebula.
Another final tweak to the image was to bring out the IFN a bit better, by a very selective brightening of only the lightness levels where the IFN is visible. Again a subtle effect, but overall bringing out the dusty area just a bit better.
The full processing workflow was as is shown below.
Processing workflow (click to enlarge)
This image has been published on Astrobin.
