Capturing the Crescent Nebula: A Bortle 8 Triumph with GraXpert and Photoshop

Astrophotography under light-polluted skies can be a challenge, but with the right equipment and processing techniques, breathtaking results are still achievable. Today, I'm excited to share my recent capture of the Crescent Nebula, a stunning emission nebula in Cygnus, imaged from my Bortle 8 backyard.

This particular capture was a great learning experience, especially when it came to image stretching. I discovered that GraXpert's automatic stretch feature actually yielded better results than my usual manual stretching in Photoshop. While Photoshop is still crucial for final touches, GraXpert really helped bring out the details in this challenging target.

The Imaging Setup

Here's a look at the gear that made this shot possible:

• Telescope: Meade LX10 8" SCT
• Focal Reducer: f/6.3 focal reducer
• Filter: Svbony Sv220 HαOIII dual narrowband filter
• Camera: ASI585MC Pro
• Location: Bortle 8 skies

Acquisition Details

All data was acquired using SharpCap with the following settings:

• Exposure: 3.77 seconds per frame
• Gain: 295
• Calibration Frames: 30 flats, 50 bias frames
• Binning: 2x2 binning

Processing Workflow

My processing journey involved a few key steps:

1. Stacking: The Hα and OIII data were separated and stacked using Siril's dedicated HαOIII splitter script. This ensures optimal alignment and noise reduction for each wavelength.
2. GraXpert Processing: This is where the magic happened for stretching. I used GraXpert for:
   • Background extraction
   • Object and star deconvolution
   • Denoising
   • Crucially, a 10% stretch. This initial stretch was instrumental in preserving detail.
3. Siril Adjustments: Siril was used for color calibration and resampling to refine the image before moving to Photoshop.
4. Photoshop Final Touches: In Photoshop, I performed the final tweaks to bring out the best in the nebula:
   • Adjustments to levels and curves
   • Sharpening
   • Camera Raw filter settings for overall color and detail enhancement.

The Result

Here is the final image of the Crescent Nebula:

I'm really pleased with how the Crescent Nebula turned out, especially considering the Bortle 8 skies. The dual narrowband filter allowed me to capture the essential emissions, and the combined processing power of GraXpert and Photoshop really brought out the intricate structures of this beautiful celestial object. It's a testament to how even with light pollution, dedication and the right tools can lead to rewarding results in astrophotography.