M27

M27 (also known as Dumbbell Nebula) is a planetary nebula in constellation Vulpecula with an apparent diameter of about 16 arcmin.

M27 (Dumbbell Nebula) in false colors (OHS)
This image is a false color composite where [OIII] is mapped to red, H-alpha is mapped to green and [SII] is mapped to blue. Stars are partially subtracted using continuum images.
M27 (Dumbbell Nebula) in false colors (SHO)
Here [SII] is mapped to red, H-alpha is mapped to green and [OIII] is mapped to blue. This view makes the very faint sulfur structures (yellow to red) better visible than the image above. Due to the bad SNR of this channel, the image only emphasizes the bright inner structure which has a diameter of about 7 arcmin. Most sources state this as diameter of M27, but the nebula is indeed much larger.
M27 (Dumbbell Nebula) in false colors (HO)
This is a false color view which only uses H-alpha (orange) and [OIII] (bluish cyan) data which have a much better SNR than [SII]. This picture shows the true size of the nebula.

Image data

FOV: 0.31° × 0.31°
Date: 2020
Location: Pulsnitz, Germany
Instrument: 400mm Newton at f=1520mm
Camera Sensor: Panasonic MN34230
Orientation: North is up (approximately)
Scale: 0.8 arcsec/pixel (at full resolution)
Total exposure times:
H-alpha (3nm): 10 h
[OIII] (3nm): 8.8 h
[SII] (3nm): 15 h
NIR: 0.7 h
Blue: 0.7 h

Image processing

All image processing steps are deterministic, i.e. there was no manual retouching or any other kind of non-reproducible adjustment. The software which was used can be downloaded here.

Image processing steps where:

  1. Bias correction, photon counting
  2. Dark current subtraction, flatfield correction, noise estimation
  3. Alignment and brightness calibration using stars from reference image
  4. Stacking with masking unlikely values and background correction
  5. Extracting stars from the emission line images using information from continuum images
  6. Denoising and deconvolution both components (stars and residual)
  7. RGB-composition
  8. Dynamic range compression using non-linear high-pass filter
  9. Tonal curve correction

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