Deep Sky Photography with digital cameras

CCD Astrophotography by Jürgen Stein

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M81, M82 and the Galactic Cirrus

M81, M82 and the Galactic Cirrus

The M81 group of galaxy is quite similar to our local group. The central galaxy is the large bar spiral M81. M82 is the brightest Infrared galaxy of the sky just 125,000 light years away from M81. A close encounter of both galaxies took place about 600 million years ago. As a result star formation is still ongoing today. Several Supernovae explosions have created strong winds that transport hot gas out of the center of the galaxy forming Hα filaments. The hot matter cools down and part of it falls down to the center again. M81 shows no signs of the encounter.
East of M81 the galaxy UGC5336 (Holmberg IX) appears as a weak patch. NGC3077 can be seen near the edge of the image. Both galaxies as well as PG28731 belong to the M81 group. Most of the other diffuse spots are remote galaxies in the background of the group.
The whole image is covered with a very faint nebula sometimes called IFN or Integrated Flux Nebula. Nevertheless “Galactic Cirrus” may be a better name for these faint structures that can be seen on many locations in the sky. They were discovered visually and photographically by Johann Georg Hagen in the 1930years. It is believed that the galactic cirrus consists of gas and dust reflecting the light of our galaxy. Some of the faint clouds that can be seen in the image are intergalactic rims between M81 and M82.

Very faint objects like IFN can normally not be photographed from light polluted areas especially when they radiate light more or less uniformly over the visible spectrum. Only with a combination of a fast telescope and very long exposure times such objects became visible.

Image orientation: North is on the right side.

Date:.2011
Telescope: Pentax SDHF 75mm @ 6.7 on Losmandy G11 mount
Camera: Moravian G2-8300FW @ -25“C.
Exposure: LRGB with L = L + B + Hα, R = R + Hα. L - 104x600s, Hα - 39x600s, R - 25x300s, G - 32x300s, B - 29x300s. No binning. Total exposure time 31h.
Location: Rhein-Main area, Germany.
Processing: Pixinsight