The Integrated Flux Nebula (IFN) near M81 and M82

The Integrated Flux Nebula(e) is a complex of galactic dust nebulae that are illuminated not by a single star or a group of stars, as is the case with most nebulae, but by the energy from the integrated flux of all the stars in our galaxy, the Milky Way. The strongest color component is blue, but some reddish patches can also be found.

Since these nebulae are extremely faint and elusive, they are not visible to the naked eye, but can be detected only in long-exposure photos of areas of the sky located far away from the galactic plane. The brightest portions of these nebulae can be found at very northerly declinations, namely in the Little Dipper and the Big Dipper. The most photographed portion is probably the one close to the M81 and M82 galaxies, both thanks to its (relative) intensity and the proximity to the two galaxies, which makes for a very nice field of view.

Because of its very low brightness, the IFN calls for very long exposures, dark skies and very careful processing: for these reasons, it’s very hard to shoot. I already tried to image this part of the sky a few years ago, but didn’t manage. A second attempt made in late December 2016 was finally successful.

Since I’m no expert in processing this kind of objects, I had a very hard time trying to bring out the faint tendrils of the nebula. Moreover, the large field of view (about 4.1 x 2.8 degrees with a full-frame DSLR and a 500-mm refractor) produced some nasty gradients very difficult to tame during post processing.

Anyway, here you go (I strongly recommend clicking the image below to bring up a higher resolution version):

IFN (Integrated Flux Nebula)

IFN (Integrated Flux Nebula)

Below is an annotated version of the image. Note Holmberg 1 (aka PGC 27605 or UGC 5139), an irregular galaxy shining at about 13th mag.

IFN (Integrated Flux Nebula)

IFN (Integrated Flux Nebula), annotated version

Main acquisition details: unmodified Canon DSLR at the prime focus of a Pentax 75 refractor (500 mm FL), 69 x 5 min. + 31 x 10 min. exposure time (totaling almost 11 h) at 1600 ISO. Processing in PixInsight and Photoshop.

My photo has some flaws, namely: the framing could be better (M81 is almost cropped out), the stars show some trailing and are a bit “splotchy” from heavy noise reduction. On the other hand, there is a whole lot of detail, so all in all I can be quite happy with the result.

Enjoy! :mrgreen:

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