SH2-254 thru SH-258

The nebula complex lies on the border between constellations Orion and Gemini and is a part of the GEM OB1 molecular cloud. Further details can found below the image.

Click on the images for a full scale version.

SH2-254 thru SH-258
This image is a false color composite where [SII] is mapped to red, H-alpha is mapped to green and [OIII] is mapped to blue. Stars are partially subtracted using continuum images.

The three larger nebulae are (from right to left) SH2-254, SH2-257 and SH2-255. The smaller nebula below SH2-254 and SH2-257 is SH2-256. SH2-258 is the small reflection nebula on the left side which appears magenta (due to the color factors). The distance of the ionizing sources of the emission nebulae can be queried from the Gaia DR3 database:

NebulaSourceDistance in light years
SH2-254HD 253247 6500 ly (± 300 ly)
SH2-255LS 19 6700 ly (± 400 ly)
SH2-2562MASS J06123651+1756548 6150 ly (± 200 ly)
SH2-257HD 253327 5150 ly (+5000/-2000 ly)

In the image SH2-254 seems to lie behind SH2-257.

Image data

FOV: 0.47° × 0.33° (full view)
Date: 2019-2021
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): 8.0 h
[OIII] (3nm): 14.1 h
[SII] (3nm): 10.9 h
NIR: 0.6 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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