SUPERCEDED - M81, M82 and the Integrated Flux Nebula
SUPERCEDED - M81, M82 and the Integrated Flux Nebula
SUPERCEDED - M81, M82 and the Integrated Flux Nebula
While many astronomical images show nebulae that are illuminated by the light from nearby stars or star clusters, this image shows an entirely different kind of reflection nebula. Surrounding our Milky Way galaxy are large clouds of dust, hydrogen, carbon monoxide, and other elements that have been ejected from our galaxy. The clouds are not illuminated by stars, but are illuminated by the entire light of the Milky Way Galaxy. Because of this, they are known as the Integrated Flux Nebulae or IFN - meaning that their light comes from the combination of all the light from our galaxy.

These clouds are mostly visible at high galactic latitudes - those portions of the sky that are well outside of the plane of the Milky Way. We see very large portions of the IFN in the regions towards the north near Polaris and other circumpolar constellations.

This image shows the IFN known as the "Volcano Nebula" or MW3 (Mandel-Wilson Catalog of Unknown Nebula #3). This nebula appears in the direction of the commonly photographed galaxies M81 and M82, both of which are featured at the center of this image. The IFN is extremely faint, and I have processed this image so as to brighten this faint nebula to show it better.

Also shown in this 6 degree by 4 degree field of view are several other northern galaxies. Immediately above and almost touching M81 is its satellite galaxy, Holmberg IX. Above M81 and M82 is the Seyfert galaxy, NGC 3077. It is a member of the M81 group of galaxies. To the lower left of M81 is NGC 2976, an unbarred spiral galaxy. On the far right edge are two more galaxies, NGC 3077 (top), an emission line galaxy that is also a member of the M81 group, and the spiral galalxy NGC 2985.

Because the IFN is so faint, I photographed this widefield image for a total of 17 1/2 hours with my 200mm Canon lens. Then, in order to show better detail within M81 and M82, I composited the widefield image with images I previously captured through my telescope. For M81, I used 9 hours of telescopic data, and for M82, I used 2 1/2 hours. As such, this image represents a total of 29 hours of image capturing!

In this image, North is to the right.

Exposure Details
Lens Canon EF 200mm f/2.8L II USM
Focal Length 200mm
Focal Ratio f/3.5
Mount Schaefer GEM - 7 1/2 Byers gear
Guiding ONAG On-Axis Guider, Lodestar autoguider, PHD Guiding
Camera Canon 450D - Gary Honis modified
Exposure 88 subs of 600 sec @ ISO 800, 58 x 180 sec @ ISO 800 for the base image (17 1/2 hours), plus M81 and M82 detail image exposures
Calibration 20 darks, 30 flats, 30 bias
Date 2/16/12, 2/28/12, 3/2/12, 2/4/13, 2/6/13, 2/9/13
Temperature 34F-2/16, 30F-2/28, 43F-3/2; 43F-2/4, 37F-2/6, 25F-2/9/13
SQM Reading 21.4-2/16, 21.2 2/28, 21.3-3/2/12; 21.7-2/4 and 2/6, 21.5-2/9/13
Seeing 3/5 on 2/16/12 and 2/28/12, 4/5 on all other nights
Location Pine Mountain Club, California
Software Used Images Plus 5.0 for camera control, calibration, stacking, digital development, star shrinking, smoothing and noise reduction. Photoshop CS5 used for levels and curves, high pass filter, star shrinking, screen mask invert, lab color, saturation adjustments, selective color, and match color. Gradient Xterminator for gradient removal. Carboni Tools for additional noise reduction, and smoothing. Registar for aligning stacks and composites and for color channel alignment.
Notes I'm extremely happy with how well this image looks. Knowing that the IFN is quite faint, I wasn't sure that my skies were dark enough to capture it at all. When I first combined all my data, I was concerned because the IFN was barely visible. However, using a handful of processing tricks, I was able to coax it out of the background and show this beautiful feature of the northern sky.

This image represents my deepest image to date - the base image is 17 1/2 hours with a very fast lens (f/3.5). I truly enjoyed this target, as it was very challenging to bring this image together.

This image was published by Astronomy Magazine as its Picture of the Day for April 7, 2016.

This image won 1st place in's Easy - Widefield category for February 2013.

My friend, Blair Macdonald, used the data from this image for his article "Imagers Corner-Multi-mask Stretching" in the August 2014 issue of The Journal of The Royal Astronomical Society of Canada. In this article, Blair demonstrated techniques for bringing out very faint features in astrophotographs.

If you liked this picture, you might also want to view:

M81, M82 and the Integrated Flux Nebula Mosaic