Object Information

The Rosette Nebula is an HII region in the constellation Monoceros. The nebula, designated here as NGC 2237, is split into several designations for its different constitutent parts. They are NGC 2237, NGC 2238, NGC 2239, NGC 2246, and the open star cluster in the centre is NGC 2244.

The stars in this cluster were formed from the nebula's gas. Studies have revealed that the central cluster was the first to form, and the radiation from these new stars generated pressure waves throughout the rest of the nebula, inciting further star formation. Thus, all the other clusters within this nebula were formed after the central one. X-ray examination of the nebula suggests that star formation is still ongoing.

The object is approximately 1.3° in diameter, making it appear nearly three times larger than the Full Moon in the sky. It is about 130 light-years across, and lies 5,000 light-years from Earth.

Image Information


This image was taken during a waxing gibbous Moon phase. Half the data is saturated with moonlight; the other half had no such issue. Tracking error was minimal or nonexistent in all subframes.


  • Canon T3i (modified: missing IR cutoff)
  • SkyWatcher NEQ6 Pro (Guided: Orion StarShoot, PHD2)
  • Skywatcher 80ED (600mm f/7.5)


  • 71x 5min exposures @ ISO-1600 (5h 55min) ~0°C
  • 12x Darks
  • 20x Flats
  • 40x Biases


Processing was done in PixInsight v1.8. The images were calibrated using ImageCalibration and ImageIntegration. The integrated image was then processed for colour. The luminance was extracted, and MultiscaleMedianTransform was used to reduce noise in low SNR areas, and the luminance and original were stretched. LocalHistogramEqualization was used to pull out nebula detail, and HistogramTransformation reduced the sky background. MorphologicalTransformation was then used to reduce star sizes, and light noise reduction using ACDNR was performed. Details were then sharpened using UnsharpMask, and the star sizes were once again reduced slightly using the same technique.

On the original image, TGVDenoise was used to prevent chrominance noise, and the synthetic luminance was then combined back into the original image. CurvesTransformation was used to improve contrast and colour saturation. ColourSaturation was used to remove slight purple clipping in the image, and the image was cropped to remove bad edges.


Data was collected on the night of December 1, 2014, at the Torrance Barrens Dark Sky Preserve in Ontario, Canada. This is a Bortle 4 site.