The Heron Galaxy / NGC 5394 + 5395 / ARP 84

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Menno555
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The Heron Galaxy / NGC 5394 + 5395 / ARP 84

Post by Menno555 »

The Heron galaxy (NGC 5394 + 5395 / ARP 84)
Distance: around 160 million lightyears
Surface brightness around magnitude 13.
Apparent size in the sky is roughly 3 Jupiters in a row

Full 3000px resolution here: https://i.ibb.co/wz42DK2/ARP84-Heron.jpg
In total 8 hours integration time.

A pair of galaxies (NGC 5395 left and NGC 5394 right) in the process of colliding. They suspect that the two galaxies already did collide once, resulting in star forming regions. The bright blue in the lower part of NGC 5395 and in the left arm of NGC 5394 are such regions.
Most likely these galaxies will have their gravitational dance for a couple of billions of years before they merge.

This capture is borderline of what my set up can handle when it comes to oversampling and tracking times.
Also tried the Optolong L-eXtreme filter to capture the present Ha but that was too much to asked :) Did add the data though.
The processing was a real battle of balance between noise, sharpness and color. Also because there are a lot of background galaxies visible.
And like usual I did not "perfected" it with too much denoising and sharpening. For me it's showing captured data and my setup does has it's limits. For me it feels a bit like "cheating" to let it look like something that my setup is not capable of. Plus the real faint stuff gets destroyed or deformed by it.
The fact that I am in Bortle 7 also doesn't help that much but I'm very satisfied with the result smile.gif

Bortle 7
Meade LX200 8" f/10 ACF OTA
Ioptron CEM25EC mount (no guiding)
Baader IR/UV Cut filter
Optolong L-Pro filter
Optolong L-eXtreme filter
Zwo ASI071MC Pro camera

Captured with SharpCap Pro @ -10 Celsius / White balance R50 B50
IR/UV Cut: 46 x 300 sec / Gain 0 / Offset 4
L-Pro: 12 x 600 sec / Gain 0 / Offset 4
L-Pro: 4 x 900 sec / Gain 0 / Offset 4
L-eXtreme: 7 x 600 sec/ Gain 200 / Offset 10

Stacked with DeepSkyStacker
Stacked everything in one go in groups with each group it's own calibration files

Processed with Siril and Photoshop
Siril: Background Extraction and Histogram
Photoshop: Curves, Levels, Camera Raw Filter (blacks, color saturation, clarity, noise reduction, sharpening)
The Heron Galaxy
The Heron Galaxy
ARP84-Heronsha.jpg (637.54 KiB) Viewed 341 times
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oopfan
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Re: The Heron Galaxy / NGC 5394 + 5395 / ARP 84

Post by oopfan »

Really great, Menno! This is very small in my refractor, together with my larger than normal pixel size, this galaxy is totally off-limits. Last year I captured some test exposures. I gave up before getting started :(
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Menno555
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Re: The Heron Galaxy / NGC 5394 + 5395 / ARP 84

Post by Menno555 »

Thanks Brian!
If I remember right, you posted about that and put out a challenge for others to capture it. And that was my first go back then at an object like this :)
That was this one. Other camera but rather a difference over a year.

Menno
NGC 5394-5 Heron.jpg
NGC 5394-5 Heron.jpg (236.54 KiB) Viewed 328 times
timh
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Re: The Heron Galaxy / NGC 5394 + 5395 / ARP 84

Post by timh »

That is a really nice image Menno. Also an object that I haven't had a go at yet and a good one to add to the list for darker nights and the return of galaxy season.

The failure to detect any HA is likely due to redshift versus the 7 nm bandwidth of the Lextreme filter ? At 160 M ly the redshift (not accounting for peculiar velocity) would be expected to be about 8nm for the HA transition just based on Hubble flow. So the HA peak then at about 664nm would likely fall beyond the longwavelength limit - ~ 659.5 nm, of the L extreme filter ? It is actually quite a cool observation because while you know the galaxy is active and must be shining in HA because of the galaxy interaction the very fact that you can't see any HA is an indirect way of telling that the Universe is expanding.

best wishes
TimH
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Menno555
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Re: The Heron Galaxy / NGC 5394 + 5395 / ARP 84

Post by Menno555 »

Thanks Tim!
The Ha is there, and the cores are showing in it. But it might be that the 7nm is just not catching the active regions or my resolution is just not high enough. If you check on Google for it in images (but also on the survey in Stellarium), there is a lot of Ha there. Especially in the regions that are blue in my visible light capture.
But I was aware that due to my Bortle and equipment that might be out of reach, so it's no failure :)

Tip for when you are having a go at it: the whole area is littered with background galaxies. I did a quick check on my unprocessed capture and there are 300 of them in view easily. But cause of the processing a lot of them fade away and around 100 are visible here. For me the next time I'll capture this I am going to try to get a balance between the background and ARP 84 :)

Menno
timh
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Re: The Heron Galaxy / NGC 5394 + 5395 / ARP 84

Post by timh »

Hi Menno,

Yes certainly you have HA there. I didn't express my point very well. The L-pro filter which is broader band and much like my UHC filter looks to have caught the HA for you just fine and I can see it in your image I just find it interesting to reflect that the L-extreme on the other hand could not detect HA even in principle versus a galaxy at that distance because the HA band gets red shifted out of its pass band (i.e to > 660 nm). I had the same thing with the Coma galaxies at 340 M ly- my normal 7nm HA filter detected light of course but not HA at that distance - but in that case I was able to conveniently use an SII filter (672nm) to specifically detect the HA because the red shift at that distance is 16 nm. Unfortunately, I don't think that you can easily get narrow band filters that would detect HA for galaxies at the various intermediate distances from 80 up to about 300 M ly- but it is only an academic point anyway because broader filters such as the L-pro and UHC types do a good job anyhow. But it is interesting that the detection (or non-detection) of HA by the narrow band filters can also serve as a photometric tool for estimating the distance to active galaxies.

Tim
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oopfan
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Re: The Heron Galaxy / NGC 5394 + 5395 / ARP 84

Post by oopfan »

Menno,

Here is a new one for you: Arp 188
https://apod.nasa.gov/apod/ap210621.html
https://apod.nasa.gov/apod/ap121108.html

This is the second time it's been a NASA APOD. The first time was 2012 with a different person at the controls. I like the 2012 version. Less saturation.

Hopefully you've got a clear view west of the meridian:
https://en.wikipedia.org/wiki/Tadpole_Galaxy

Brian
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Menno555
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Re: The Heron Galaxy / NGC 5394 + 5395 / ARP 84

Post by Menno555 »

Thanks Brain for the tip!!
That indeed a nice challenge. Busy now with M101 ... well, not now. Clouds, you know ... :)
This one is for sure next, it's nice and high now.

Menno
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