Sh2-124
47’ x 31’ | 0.3”/px | 9480 × 6244 px | full resolution
Cygnus
RA 21h 38m Dec 50° 20’ | 0°
Sh2-124 is a large emission nebula in the constellation Cygnus. It is located on the northwestern edge of the constellation, along the Milky Way, east of the pair of stars ρ1 Cygni and ρ2 Cygni. Sh2-124 is an extended and enigmatic nebula system, linked to the infrared source RAFGL 2789, which is identified with its stellar counterpart known as V645 Cygni, probably an O-class star or the Ae/Be star of Herbig. The complex is probably located in the Orion arm at a distance of about 8,480 light year. The main stars responsible for the ionization of the gas in the nebula would be a blue star of spectral class O7V and a blue star of class B2V, to which other stars may be added. The nebula hosts star formation processes. Some infrared sources have been identified inside, including five identified by the IRAS satellite.
source: Wikipedia
Data Acquisition
Data was collected over 7 nights during the months of July and August 2025, using a 14” reflector telescope with full-frame camera at the remote observatory in Spain. Narrowband filters (Ha, OIII and SII, all 3nm) were used to gather the data. A total of approximately 22 hours of data was 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” Ha, OIII, SII (3nm) 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.
Intense nebulous areas are notorious challenges for background correction. And sometimes correction does more harm than good. For this one I tried MultiScaleGradient Correction again. The Ha-image was well corrected for this one, but there were no OIII or SII data in the MARS database, so those channels were corrected using GraXpert,
When reading other astrophotographers experiences with Sh2-124, there is often mention of weak signals of both OIII and SII. Some don’t even see it at all. Indeed both the OIII and SII are very weak compared to the predominant Ha signal. But during stretching with the SmartStretch scriptlet from the PixelMathGUI script, a target background is defined, which brings all three colour channels more in balance with each other. This is something to keep in mind, as in this false colour image, the ‘false’ part does not only relate to the hue, but especially also to the brightness. This is true for many Hubble Palette images and certainly for this one.
After the initial palette of false colours is established there is often a lot of pulling and pushing of brightness, hue, saturation etc. Often the CurvesTransformation tool is used for that, but this time also a couple of iterations of the GHS tool was applied. Using it for example in ‘brightness’ or ‘saturation’ mode gives a lot of selective control to manipulate very specific areas of the image. The effects show some resemblance with what can be achieved with the HSL tool (Hue, Saturation, Luminance) that is found in many non-destructive image editing software such as Photoshop and Affinity Photo.
The rest of the editing followed a pretty standard processing workflow.
Processing workflow (click to enlarge)
This image has been published on Astrobin.
