A collaboration mega-project: 225+ hours on M106!

[Francesco Meschia]

Hello SJAA imagers,

At the beginning of January a German friend of mine, Pete Maasewerd (pete_xl on Astrobin), invited me to join him in an imaging project he had in mind for a while. In 2020 Peter had imaged the M106 galaxy in HaLRGB, and he noticed that the core of this galaxy shows two faint, anomalous, spiral arms in H-alpha light. He proposed to me and to two other imagers (Philip –pmneo on Astrobin– and Andrew –Professor2112 on Astrobin) that we should try to collect as much data as possible on this target, and make those arms really pop out.

So we embarked on this quest, armed with similar rigs: an AT130EDT triplet refractor for me, and three TS130EDTs for the other three imagers. These are very, very similar 5” refractor scopes. As for cameras, it was an ASI294MM for me, and three ASI2600MMs for the other three guys. With our geographical distribution (one imager in California, one in Massachusetts, one in North Rhine-Westphalia and one in southern Bavaria), we covered a good set of climates and spanned nine time zones! Unfortunately, we also had quite a spread in Bortle zones: the two German imagers were collecting data from their Bortle 4 backyards, whereas we US imagers had to deal with Bortle 7 skies. Germany clearly must be doing something right: my friend Pete lives just 20 miles from the city of Dortmund, and yet he enjoys a Bortle 4 backyard!

Over the course of two months, we collected a lot of data. LRGB data were essentially from the German imagers and their Bortle 4 sites, whereas I contributed to the narrowband data, for which my Bortle 7 disadvantage is not so strong. After pruning the bad subs, we were left with an amazing 225 hours and 30 minutes of data: 17 hours for luminance, 8 hours for each of the R, G, and B color filters, 109 hours of H-alpha and 75 hours of O-III. Roughly 400 GB of subs. One of the imagers, Phillip, set aside 1 TB on his private cloud to pool all the data, and Pete calibrated, registered and stacked everything and released the stacks to the four of us. The idea was that each of us would then be free to process them as they saw best, and that we would “release” the final images to the public together – which happened today!

The data was amazing: so much faint detail. Processing was still challenging, because the data was so good that there was always some detail that I really wanted to bring out. I used the whole panoplia: PixInsight, StarNet V2, StarXTerminator, Photoshop CS, and Topaz Denoise. It took me probably 60 to 80 hours of work in total. The anomalous arms (see https://www.nasa.gov/centers/goddard/news/topstory/2007/mystery_spiralarms.html) are well visible, and were recorded in both H-alpha and O-III light. But maybe even more amazing is the number of other galaxies in the picture. Even leaving aside NGC 4231, NGC 4232, NGC 4217, and NGC 4226, there are almost 300 other galaxies visible against the smooth background sky, down to past magnitude 22. Next to M106 there is a cluster of galaxies that lies 3.2 billion light years away. And the picture shows quasars that are supposedly 10 billion light years from us! Be sure to check out the plate-solved and annotated version of my image – and at full resolution.

This is by far the deepest image that I had the good fortune to process. Even though my contribution was limited, due to my observing site, working collaboratively with other imagers was a great experience – definitely the way to go, if one needs to collect lots of data.

I’ll love to hear your comments on our images, and questions about the collaboration or process. Here are the links to the four images:

Andrew – https://www.astrobin.com/9cxaye/

Francesco – https://www.astrobin.com/e1xjub/

Pete – https://www.astrobin.com/2a0fxn/

Philip – https://www.astrobin.com/6wue02/

Thanks,

Francesco

[Karen Bieber]

Francesco,

Amazing photo and amazing collaboration!

Karen

<M106b-14.jpg>

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[Gary Hethcoat]

Hi Francesco,

Wow, the image is jaw-dropping!  Can you show us the location of the anomalous arms?  I'm not sure what to look for.

I assume the red-ish areas are the H-alpha data?  Can you say a few words about how that data was added to the image?  Was it just pixelmath?

It's really amazing to look at the "background" of this image and see how many small, faint galaxies are visible!  Almost like a Hubble "deep field" image.

Gary

Gary Hethcoat
gary.h...@gmail.com

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[Francesco Meschia]

Hi Gary, thanks a lot!

The anomalous arms are these:

They’re actually part of a larger, very faint structure, visible in the Chandra and VLA data in the article I linked:

We found those structures both in the H-alpha and O-III data we captured. Combining them with LRGB data was the hard part. I started by subtracting the continuum emission contribution from the two narrowband images, to increase the contrast of the pure H-alpha structures. Still, there was a huge dynamic range between the bright H-II knots of the “regular” spiral arms and these anomalous arms. If I had combined everything as-is, either the anomalous arms would’ve been invisible, or the H-II knots would’ve glowed like neon lights. I ended up creating a mask that compressed the dynamic range of the narrowband data, and using it to tame down the contrasts when using pixelmath.

Francesco

<M106b-14.jpg>

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[Gary Hethcoat]

Ah, I see now!  That's really cool.  Thanks Francesco.

Gary

Gary Hethcoat
gary.h...@gmail.com

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[Rich Klein]

Incredible image, Francesco!

- Rich

[pa...@pinger.org]

Awesome image! 

Your comment about Bortle 4 in Germany is interesting... I would have thought that entire western Europe would be bortle 8 or 9.

Pawan

[Francesco Meschia]

Hello SJAA Imagers,

In case anyone is interested, we’ll be presenting our M106 project tonight at 6:30 PM Pacific Time in The Astro Imaging Channel on Youtube. Link here: https://youtu.be/iG1srDXqycM

Francesco

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[Richard Thornton Senegor]

Hopefully this will be recorded! I'd love a link to watch later this week :) 

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[Glenn Newell]

It should be that same link.

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[Glenn Newell]

Great Presentation!

I think I even learned some Photoshop Tricks.

[Francesco Meschia]

Thank you, Glenn!

Francesco

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