Bode Galaxy, Messier 81

Johann Elert Bode was the first to discover this galaxy in 1774. Five years later it was also found by Charles Messier who put it in his catalogue. It is located in the constellation of Ursa Major some 12 million light years away from earth. 

If you look closely in the picture to the right of the galaxy you can see an irregular blue structure. This is an irregular dwarf galaxy named Holmberg IX after the Swedish astronomer Erik Holmberg (1908-2000) who described it in 1969. In the picture you can also see very faint streaks of interstellar dust that are difficult to capture with the camera. 

This image was taken over several nights between April 15 and 22, 2023. I used the ZWO 2600 MM camera connected to the Celestron 8″ EdgeHD telescope. With the luminance filter (see below) I capture details of the galaxy, surrounding structures and dust. Total exposure with this filter was 8 hours (96 x 5 min). The arms of a spiral galaxy usually contain plenty of ionized atomic hydrogen that creates nebulae and star forming regions. To capture these regions a hydrogen alpha (Ha) filter was used and I took long exposures (60 x 10 min) to get solid data. In the image these hydrogen regions are colored pink or red. Finally exposures with red, green and blue filters were used to get the colors of the galaxy (26 x 5 min for each filter).