SH2-112 - Ultraviolet vs Hydrogen

Located in the rich star fields of the constellation Cygnus, Sharpless 2-112 (SH2-112) is a magnificent emission nebula that offers astrophotographers a captivating target. At approximately 5,600 light-years from Earth, this nebula is part of the Sharpless catalog, which includes 313 emission nebulae identified in the northern hemisphere.

Science behind SH2-112

SH2-112 is primarily illuminated by BD+45 3216, an O8V-class star at its center. This star, about 30 times more massive than the Sun, emits intense ultraviolet radiation. This radiation ionizes the surrounding hydrogen gas, causing the characteristic red hydrogen-alpha emission. The circular structure of the nebula, interspersed with dark rifts particularly visible on its western side, adds to its visual complexity. (Cosgrove’s Cosmos) (NOIRLab).

With an apparent diameter of about 18 arcminutes, SH2-112 is a relatively large object in the sky, making it a rewarding target for deep sky imaging. Its proximity to the North America Nebula and its location within the dense star fields of the Milky Way enhance the photographic potential of this region.

Capturing SH2-112

Imaging SH2-112 requires careful planning and the right equipment. Here is an overview of my setup and process for capturing this nebula:

Equipment :

• Camera: QHY294M Monochrome CMOS camera

  • Telescope: : Orion 200mm f/4 astrograph

  • Mount: : Sky-Watcher EQ6-R Pro

  • Filters: :

    • Antlia Edge H-alpha 4,5nm

    • Antlia Edge OIII 4,5nm

    • Optolong SII 6nm

  • Guidage : Off-axis guider

  • Guiding Camera : ZWO ASI120MM Mini

  • Logiciel N.I.N.A. for image acquisition and PixInsight + Photoshop for processing

Data Collection :

• Total Exposure Time : about 23 hours over 5 nights

  • Details :

    • Ha : 71 x 180 seconds

    • OIII : 128 x 180 seconds

    • SII : 254 x 180 seconds

  • Calibration frames :

    • 50 darks

    • 20 flats for each filter for each night

    • 50 dark flats

Processing Workflow :

• Preprocessing : WeightedBatchPreProcessing Script in PixInsight

  • Gradient Removal : AutoDBE (SetiAstro)

  • Channel Combination : Ha, OIII and SII RGG Combination

  • Stretch : Statistical Stretch + StarStretch (SetiAStro)

  • Noise Reduction : DeepSNR (image couleur)

  • Deconvolution : BlurXterminator

  • Final Tweaks : CurvesTransformation for contrast and color balance.

Challenges

Photographing SH2-112 presented a few challenges, including managing gradients caused by slight cloud cover and collimation issues on the first nights. Despite these obstacles, the result is a richly detailed image that beautifully showcases the nebula's structure and the complex interaction of ionized gases.

Conclusion

SH2-112 is a testament to the hidden wonders within our galaxy's star fields. For astrophotographers, it offers a blend of scientific intrigue and aesthetic beauty, making the effort of capturing and processing this nebula extremely rewarding. Whether you are a seasoned astrophotographer or a dedicated amateur, SH2-112 is a target that deserves a place on your imaging list.

For those interested in diving deeper into the details of SH2-112, resources such as Cosgrove's Cosmos, NOIRLab, and other astrophotography communities provide invaluable insights and data.

Happy imaging, and clear skies!

References :

• Cosgrove’s Cosmos: SH2-112

• NOIRLab: SH2-112