wimvb

Keep it up, you're getting there. 😉

I haven't had more than a clear night since I did my version. I spent that night collecting 10 hours H-alpha data, which turned out to be a waste of time. So no need to go that route.

8 hours ago, Wanderers said:

Does the same rule apply in ap?

Basically, yes. In my experience (which is limited to deep sky photography), if you want to keep star colour, you can't have them blown out. Modern cmos cameras have enough dynamic range to allow you to keep the stars under control, while also capturing the fainter details. But, unlike daytime photography, the tatget's brightness range is also very large. To get to the really faint parts of a target, you need to capture enough data, ie a long total integration time. In each single frame, you need enough exposure so that you can't see the read pattern (bands or lines in the single frame).

So, expose for the highlights and develop for the areas in "shade".

When I started with astrophotography, I certainly spent more nights solving problems than capturing data. But the last few years, I've had very few problems. Mind you  the problems that I do encounter are more subtle. I guess that is the learning curve.

6 hours ago, ollypenrice said:

 

I do have the linear stacks but have never applied L over RGB at the linear stage because I have always wanted to process them differently, the L for deep stretch and high detail, the RGB for low noise with detail unimportant.

I'll see what happens...

Olly

That's also how I do it. Besides the different stretches, that workflow also allows me to locally enhance L without affecting the colour, and vice versa.

4 hours ago, ONIKKINEN said:

Tricky target in that case, if both are of similar brightness so difficult to say where the M63 tidal parts end and the IFN begins.

Indeed, and the authors of the paper that @dciobota links to discuss this.

double post

2 hours ago, ONIKKINEN said:

I think there could be a tiny bit of IFN around M63, but unlikely to be shown in significant amount due to its weakness

Ifn may be weak, but so is the tidal structure surrounding M 63.

9 minutes ago, dciobota said:

Thanks Gorann.  The first one looks the deepest and shows material extending way outside the area I've imaged.  That is interesting indeed.

That seems to be ifn in the fov. This makes it even harder to determine what the structures really are.

I imaged M63 last year, but because the nights were getting awfully short up here, I never bothered with luminance. Maybe I should do that this year.  https://www.astrobin.com/2wu2wj/B/

The most extensive study of the weak structures surrounding the disc of M63 is the one linked to by @dciobota in his original post. The ring structure to the NE of the galaxy is undoubtetly a tidal stream due to a galaxy accretion event. Features to the South and SW are considered to be of uncertain sources, such as the extended disc and halo of M63 (spiral arms as Olly suggests), and possible (older?) accretion events.

On 16/02/2024 at 06:37, dciobota said:

Could there be star streams that dispersed and faint to be picked up like that?

According to the study you linked to in your original post, tidal disruptions caused by older merger events get dimmer over time. The authors of the article speculate about the possibility that there may have been several merger events, with the more distinctive loop to the NE being the most recent.

All in all, extremely cool physics, which makes yours a darn pretty picture, if you ask me.

3 hours ago, dciobota said:

Btw Wim, I totally forgot to thank you for that book.  I'm going to look into it as this discussion and that article has definitely gotten my curiosity going

You're welcome. 

4 hours ago, dciobota said:

My skies are bortle 4-5

That's fairly dark, and the 17 hours you spent on this image shows that your skies are good enough to catch tidal streams.

1 hour ago, dciobota said:

So maybe then my background isn't actually real?  Could there be star streams that dispersed and faint to be picked up like that?

Oh and dopey me totally forgot to invert the image.  I'll do that tomorrow.

Galaxy collisions, which is what this is about, are very complicated processes. Detecting their products sets very high demands on our equipment, data acquisition and data processing. Even then, we do astrophotography at the very limit of what can be achieved with moderate amateur equipment. (You haven't mentioned what equipment was used to capture this image, but my guess is that it wasn't a multi-telescope rig situated in the New Mexico desert.) But, from what I've seen here so far, your result certainly looks real.

Btw, to learn more about the science and theory of galaxy collisions, I can recommend this book. It helped me to get a better understanding of the subject.

https://link.springer.com/book/10.1007/978-0-387-85371-0?utm_medium=referral&utm_source=google_books&utm_campaign=3_pier05_buy_print&utm_content=en_08082017

2 hours ago, ollypenrice said:

Maybe we could ditch the dismissive term 'pretty pictures?' If so I'd be more than interested in joining the conversation.

Olly

Please do join the conversation.

5 hours ago, michael.h.f.wilkinson said:

The blue ellipse in the paper is due to H-I (neutral hydrogen at 21 cm wavelength). I am not sure how much that region would show up in the optical wavelengths. I would certainly not expect star-forming regions there, but there may be stars, of course. 

Neutral hydrogen wouldn't show up. But it's usually not just gas that is ripped from a galaxy, but also stars and dust. It's just that radio telescopes are sensitive to it, while optical telescopes can pick up the star streams. Anyway, there's some very cool physics going on here.

Very impressive. I think that what you have is real. R.J. Gabany and David Martinez-Delgado are both authorities in the field of very deep field astrophotography.

One tip: in order to see what is in an image, I usually invert the linear L and "superstretch" it by bringing in the black point and the white point until I can see all features, including ugly artefacts from imperfect flat calibration and such. Inverting the image makes it easier to see faint differences in signal.

I see a staircase mosaic int the making. "Not because they are easy, ..."

Nice! How dark are your skies? Officially  I'm in a Bortle 5 zone, but with all the snow, it seems brighter than that. I'm looking forward to your 20 hours version. I still plan to add Ha to my image. 10 hours might do it, but probably more.

2 hours ago, WolfieGlos said:

Wow, that must be a faint one if those arms are only just showing up after that time.

Believe you me, it is.

I just saw your image on Astrobin; impressive. I'd like to image a gravitational lense at some point, but my sky conditions make it almost impossible. Where (above the clouds) do you image from?

7 hours ago, windjammer said:

You could always try a barlow as an experiment

I only have a few cheap SkyWatcher 2× barlows in my (also cheap) eyepiece kit. Shooting at bin 1 will be easier.

4 hours ago, tomato said:

That’s a debate I’m still having. I have sort of settled on my Esprit 150/ASI 178 combination for small targets, but I still  get the urge to trade the refractor in for a 14” or 16” RC and mate this to a IMX571 sensor and go galaxy hunting at around 0.5” per pixel, but then common sense prevails, knowing my sky can never do this justice.

With my MN190/ ASI294MM combo, I always use bin2 at 0.95"/p, but I could try bin1. It's just that the files become so large (97 MB), and the camera specs are a lot poorer.

Very nice, especially with the addition of Oiii. In my own experience, I find that galaxy images gain a lot when narrow band is added. Unfortunately, I don't have room for an additional filter in my filter wheel.

Very nice, Göran. I had to look this one up. It must be a lot fainter than what your image suggests here. That's quite a stereo photon hoover that you have in your backyard.

57 minutes ago, tomato said:

Great work!

I have looked at Adam Block's image in the Cambridge Photographic Atlas of Galaxies (660 mins integration, 800mm reflector, SBIG STX-16803 from Mount Lemmon SkyCenter) and you have lots more detail in the spiral arms , all those hours make a difference!👍

Thank you, Steve. All those hours were needed, believe me. But Adam's still wins in some regards. Aperture, focal length, and seeing do still make a difference. I sometimes I wonder if a longer focal length and a finer imaging scale would give more detail. Not on paper, probably. But theory isn't everything.

@windjammer  check this link

https://pixinsight.com/examples/M31-Ha/index.html#Continuum_Subtraction

I found a thesis from 2014 which discussed the interaction of ngc 2460 and ic 2209. In it was an image of the pair, so I compared it to my result. It seems that I resolved details down to about 24 Mag/arcsec2. Not too bad for a simple 190MN in a Northern European backyard.

Ludwig, J. A Survey of Dwarfs and Tidal Debris around Nearby Massive Galaxies – Deep Imaging with Medium-Sized Telescopes, 2014

http://www.ub.uni-heidelberg.de/archiv/17232

14 hours ago, lrh said:

Amazing work - I always love seeing images of active galaxies! Great point about the star formation. It's also worth mentioning that active galactic nuclei also produce a lot of Halpha emission (both from the nuclei themselves and due to them ionising the central regions of the galaxy), so I'm guessing that the Halpha subs will bring out even more central detail in the main galaxy.

Looks like you captured quite a few background galaxies too!

Luke

11 hours ago, Stargazer33 said:

That's beautiful Wim! The detail & sharpness you have achieved is wonderful to see. I love the colour in ic 2209.

4 hours ago, WolfieGlos said:

Nice image Wim, worth the 30H for this 🙂 Loads of background galaxies too, look forward to the Ha addition.

I take it that you've managed to pull out IFN across the field as well?

Thanks, all.

@lrh, the problem with extended H-alpha is that it tends to produce pink galaxy cores, if not checked. But once I have enough H-alpha data, I'll figure out how to best incorporate it. My usual method is to use red continuum subtraction, which isolates the knots in galactic arms.

@WolfieGlos, I think that I will need at least 10-15 hours of H-alpha. Fortunately nights are still long "up here". And yes, there is some ifn in this area, though not as strong as around M81/M82. The bright cloud on the left hand side is a combination of ifn and the glow of a nearby star.

ngc 2460 lies at a distance of about 70 million light years in the constellation Camelopardalis. The galaxy has an active nucleus and is believed to be interacting with its smaller neighbour ic 2209 (to the right). The arms of the larger galaxy are thin and extend very far, which makes this galaxy a very difficult target. It took 30 hours of exposure time to separate the galaxy arms and the surrounding dust from the noise.

If the weather allows, I will try to add H-a to the galaxies. Interacting galaxies tend to have massive star formation, which the bright blue colour of ic 2209 also hints at. These galaxies usually have bright H-alpha clouds, where the star formation occurs, and more often than not, it pays off to spend a few hours on targets like this with a H-a filter in front of the camera. This is often overlooked by astrophotographers.

Equipment:

SkyWatcher 190MN on an AZ-EQ6

ZWO ASI294MM camera with Optolong LRGB filters

Exposures:

Luminance: 327 x 3 minutes

RGB: 68 + 47 + 53 x 5 minutes