NGC 2611 is a large cloud of gas and dust, visually located in the constellation Monoceros. The nebula is illuminated by the very bright star, R Monocerotis the bright star a bit hidden by the nebula, buried in the vertex of the fan).

The fan shape is interesting, but what makes this nebula special is its variability--it changes brightness constantly. Scientists are not sure what causes this variability, but perhaps it is caused by a dense cloud of gas coming between the star and the nebula, changing the amount of light hitting the nebula. If I remember, I'll image it again next year, to see how different it is.

The field is thought to be about 2,500 light years from Earth; at that distance, the nebula is about 1 light year long. Visually, this field is about the width of a full moon (although very dim by comparison).

Technical Information:

L:R:G:B: 540:180:165:200 (a total of almost 18 hours of light-frame exposure time); here's a chart showing the various subexposures I used in the image:

Luminance: 32 fifteen-minute, and 20 three-minute
Red: 12 fifteen-minute
Green: 11 fifteen-minute
Blue: 10 twenty-minute

Equipment: RC Optical Systems 14.5 inch Ritchey-Chrétien carbon fiber truss telescope, with ion-milled optics and RCOS field flattener, at about f/9, and an SBIG STX-16803 camera with internal filter wheel (SBIG filter set), guided by an SBIG STX guider, all riding on a Bisque Paramount ME German Equatorial Mount.

Image Acquisition/Camera Control: Maxim DL, controlled with ACP Expert/Scheduler, working in concert with TheSky X.

Processing: All images calibrated (darks, bias and sky flats), aligned, combined and cropped in Pixinsight. Color combine in Pixinsight. Some finish work (background neutralization, color calibration, noise reduction with NoiseXTerminator; deconvolution using BlurXterminator, HDR combine of the luminance data) done in Pixinsight; some cleanup finish work was done in Photoshop CC.

Location: Data acquired remotely from Sierra Remote Observatories, Auberry, California, USA.

Date: Images taken on many nights in late November 2025. Image posted April 29, 2026.

Date: Image scale of full-resolution image: 0.56 arcseconds per pixel.

Seeing: Poor

CCD Chip temperature: -25C

Copyright 2025, 2026 Mark de Regt

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