The Dumbbell Nebula (M27) Imaged in SHO

This image showcases the Dumbbell Nebula, also known as Messier 27 (M27), captured using the narrowband SHO (Sulfur II, Hydrogen-alpha, Oxygen III) color palette. Despite being a significant crop, the image reveals the intricate details within the nebula's core.

Equipment and Software

This capture was made possible with a dedicated astrophotography setup:

• OTA: Stellarvue SV105T w/0.8x reducer (588mm fl at f/5.6)
• Mount: ZWO AM5N
• Imaging camera: ZWO ASI1600MM-Cool
• Guiding camera: ZWO ASI120MM OAG

The workflow involved the following software:

• Capture: NINA
• Guiding: PHD2
• Processing: PixInsight

Acquisition Details

• Location: Joshua, TX (Bortle 4)
• Dates: 2025-06-28, 2025-06-29
• Gain: 200
• Offset: 50
• Camera Temp: -10°C
• Filters:
  • Sii: 30x300" Astrodon 3nm
  • Ha: 32x300" Astrodon 5nm
  • Oiii: 30x300" Astrodon 3nm
• Total Integration Time: 7 hours 40 minutes
• Calibration Frames: 64 darks, 30 flats, 200 bias per calibration set.

Processing Workflow

The image underwent a detailed processing pipeline:

Preprocessing

• Batch PreProcessing script for calibrated images.
• Star Alignment.
• Image Integration.
• 2x Drizzle Integration.
• Dynamic Background Extraction.
• Dynamic Crop.

Luminance Processing

• Stacked Ha and Oiii subs (without rejection) to create the Luminance layer.
• Applied BlurXTerminator and NoiseXTerminator.
• ArcsInhStretch for initial stretching.
• Histogram Transformation.
• Created a starless version using StarXTerminator.
• Combined the starless version with the image using a custom PixelMath expression for enhanced detail retention.
• Further refined with MultiscaleLinearTransform and HistogramTransformation.

Narrowband Masters (SHO)

• Individual Sii, Ha, and Oiii linear masters were prepared:
  • Applied BlurXTerminator, NoiseXTerminator, and StarXTerminator.
  • ArcsInhStretch for initial stretching.

SHO Combination and Tonemapping

• Combined the prepared Sii, Ha, and Oiii masters using ChannelCombination (R: Sii, G: Ha, B: Oiii) to create the initial SHO tonemap.
• Tonemap Processing:
  • HistogramTransformation with masks for controlled stretching and color balance.
  • GeneralizedHyperbolicStretch for contrast enhancement.

Final Integration and Adjustments

• Combined the processed SHO tonemap with the Luminance layer using LRGBCombination.
• Applied LocalHistogramEqualization.
• CurvesTransformation for final color and contrast adjustments.
• A masking technique involving Invert > SCNR > Invert was used to address and minimize magenta color casts.

This result highlights the power of narrowband imaging in revealing the hidden structures and colors of celestial objects. The Dumbbell Nebula, with its intricate shells and cores, is a prime target for such techniques.

For more details and to view the image on Astrobin, Flickr, or Instagram, please visit: