NGC 2261 (Hubble’s Variable)


    NGC 2261 (also called Hubble’s Variable Nebula) is a reflection nebula located in the constellation Monoceros. The nebula is illuminated by the giant B0 star R Monocerotis (R Mon). This star cannot be seen directly but is hidden in the nebula.

    The nebula presents rapid changes to its shape and internal structures. Hence, pictures from different years will deviate from each other. The reason for this is most likely not a substantial change to the nebula itself but rather small variations of the matter close to the light source R Mon, which cast shadows onto the more distant areas of reflection matter.

    Right above NGC 2261, a faint but clearly red object can be glimpsed. This is the Herbig-Haro object HH 39. The dark starless area in the upper left corner of the image is LBN 922.


  • Date: 28 December 2019 – 2 January 2020
  • Location: Bergisches Land
  • Exposure: L: 29x300s / RGB: 12x300s each (total: 5.4 hours) @ Unity Gain
  • FWHM: 2.4-3.8″
  • Note: Image is downsampled to 75% (1.21″/px)
  • 100% Crop: Crop in full resolution (0.91″/px)
  • Telescope: APO Esprit 120ED f/7
  • Mount: Paramount ME MKS5000
  • Camera: Alccd-QHY163m + QHY-FW
  • Filters: Baader LRGB