IC434, Horsehead Nebula

10 January, 2024
mono broadband nebula

Acquisition Details

IC1848 R G B
Frames 53 19 17 17
Exp. time 300s 300s 300s 300s
Flats 20 20 20 20
Darks 20      
Bias 15      

Final Masters



This is 🐴 IC434 🐴 mostly known by its other name: the Horsehead Nebula.

Ever seen those three almost perfectly aligned stars in the night sky during winter? The lowest star (seen from the northern hemisphere) is surrounded by a massive hydrogen cloud where stars can be formed and has a diameter of 1500 light years.

Shot this image using a Hydrogen-alpha (Hα) filter and regular red, green and blue filters.

Merging H-alpha with RGB data

This image needed a different approach. Since IC434 contains lots of Hydrogen, I shot with a Hydrogen filter rather than a Lumminance filter. This way I could filter out the details of the nebulae. After combining red, green and blue channel data, normally, you’d merge it with luminance data. Instead, I merged the hydrogen data with the red channel using PixelMath. For this, the following statement was provided on the red channel:

# PixelMath
B: $T
G: $T
R: $T * 0.05 + Hα * 0.95

Below you can see the H-alpha master file I used


H-alpha Inverted

For most of the narrowband images I create an inverted image as well. This way details are more visible than normal. Below is the inverted Hα-master.


Astrometry Calibration

Astrometry Job 9023077
Center (RA, Dec) (84.980, -2.646)
Center (RA, hms) 05h 39m 55.081s
Center (Dec, dms) -02° 38’ 45.103”
Size 2.57 x 2.57 deg
Radius 1.819 deg
Pixel Scale 1.56 arcsec/pixel

Data Processing

Processing was done in PixInsight only. Steps of the process are listed below:

  1. DynamicBackgroundExtraction on separate channels,
  2. LRGBCombination on only RGB channels
  3. SPCC,
  4. Merging Ha with Red channel on RGB image using expression: $T * 0.05 + Ha * 0.95
  5. Rerunning SPCC again for exact spectral match of stars and therefor enhancing red channel,
  6. BlurXTerminator on the HaRGB-channel for correcting stars and nebulae
  7. SNCR noise reduction (0,70) to reduce green noise,
  8. BackgroundNeutralization to make sure background is correctly calibrated
  9. Stretched the image using HistogramTransformation
  10. DarkStructureEnhance on the image (0,40) to enhance horsehead nebula
  11. StarXTerminator (splitting stars and background),
  12. Adjustments with CurvesTransformation
  13. NoiseXTerminator on the starless image using masks for separate background and galaxy noise reduction
  14. Merging of the stars and starless image using PixelMath, expression: $T + HaRGB_stars
  15. Final adjustments with CurvesTransformation
  16. BlurXTerminator for reducing star size a bit