Mis à jour : 28 oct. 2019
Messier 109 is a barred spiral galaxy located in the constellation of the big bear, Ursa Major. It was discovered by Pierre Méchain in the year 1781.
Messier 109 occupies the second to last entry in Messier's famous catalog of deep sky objects, in between M108 (seen edge-on and photographed during Episode 12 with M97) and M31's satellite galaxy M110 photographed in Episode 4 of Galactic Hunter.
M109 looks small and is not super bright at magnitude 11. It is part of the M109 group, a group of 79 galaxies to which it is the brightest member.
Below is our image of Messier 109. We consider this a failure as we are not happy with our final image and will definitely try to get a better result another time.
This was taken soon after switching from our Canon 7D Mark II DSLR camera to our ASI 1600MM cooled Astrophotography camera, and we had no idea what settings to use for this object. More info on that below!
We've tried to process our files several times, and you will see further down this post a version of M109 with a much smoother, less brutal processing workflow.
3 hours and 54 minutes on M109
Camera: ZWO ASI 1600mm Pro Mono
Telescope: Orion 8" Astrograph f/3.9
Mount: Atlas EQ-G motorized Mount
Acquisition: ASI Air
Total Exposure Time: 3 hours and 54 minutes
Exposure Time per frame: 3 minutes
Filters: L (1 hour) / R (1 hour) / G (1 hour) / B (54 min)
You can find M109 quite easily as it lies just next to one of the bright stars forming the Big Dipper asterism: Phecda. Due to its size and brightness, you will need great, dark skies to spot the galaxy, and it will look like a tiny fuzzy patch. We did not see any details when observing this target with our 8" Newtonian telescope. M109 looked like a medium size, slightly elongated blurry star.
WHAT DID WE DO WRONG?
Just like the other targets we captured the days/weeks after getting our CMOS camera (Thor's Helmet, M106, or the Owl Nebula & the Surfboard Galaxy), we really did not know how to pick the settings for the Gain, as well as which filters to use and what exposure time we should spend on each!
Our image of Thor's Helmet was done in 3 hours and turned out pretty great doing one hour on each narrowband filter (Ha, Sii and Oiii).
Messier 106, as well as M97 and M108 also ended up looking beautiful although we had a hard time dealing with noise in post processing. These were our first targets in RGB (+ L) and we felt like we should have lowered the gain we used for narrowband, which was set to 139.
Files stacked and ready to be processed
After talking with a couple of other astrophotographers on Instagram, we learned that we should have spent way more time on the Luminance channel rather than doing 1 hour for each filter. This makes complete sense, as R, G, and B are just useful to give color to the image, but not details.
As you can see in the acquisition details under our image, we spent about one hour on each of the L, R, G and B filters. We assume our final result would have been much better if we spent 2 or 3 hours on L and the rest on RGB.
As we mentioned in the intro of this post, we processed M109 several times, and actually never ended up with a result we were really proud of. At some point, we loaded up the files into PixInsight again and went through all our processing steps very fast without caring too much. This is something we sometimes do on purpose as the end result may sometimes be surprising in a good way.
For this target though, the final image we got is not one we will keep and proudly display anywhere. The background is a bit too dark and noisy, and the stars are over saturated and have unnatural colors. The galaxy itself though is not bad at all! There is more visible details than in our "smoothly processed" image, and the colors of the spiral arms and the core match the true colors of this type of galaxy. We sadly did not manage to obtain a result that was in-between these two images.
M109 with a more intense processing workflow
Messier 109 is not a galaxy we are very much in love with, but we sure had some long and frustrating "fun" in PixInsight trying to get a good final image of it! We initially imaged this target on a night where we found ourselves having no target in mind.
We are glad to have picked this one as it has filled the spot between M108 and M110 in our Messier Catalog!
We will revisit this object later in the future, once we feel more comfortable with our new camera.
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