NGC 55 with 9 hrs of H-alpha

[Placidus]

Ok, we've shamelessly copied Strong Mike here. Last night we added 9 hours of 2x2 binned H-alpha to our previous 28 hours of 1x1 luminance and 4 hours per channel of 1x1 RGB.

The result (big one here) (https://photos.smugmug.com/Category/Astrophotography-at-Placidus/i-qCKwzkR/0/9d3ec064/O/NGC%2055%20Ha%209hrs%20L%2028hrs%20 RGB%204hrs%20each.jpg) is once again pleasingly similar to Mike's. Pleasing in the sense that if you are doing science or something like it, and you do the same experiment, you should get the much same answer.

The H-alpha (mapped to red, and just averaged with the wideband red) produced a transformation: big swirly clouds of nebulosity against an otherwise somewhat featureless galaxy. It is still very disrupted compared with what you can see in Barnard's Galaxy or NGC 300 in H-alpha.

Oh, for the colourblind, swap the red and green channels in PhotoShop, or you won't see anything different from before.

Best,
Mike and Trish


Edit: After some discussion, we've increased the relative amount of red. The hyperlink now points to the revised version. The left hand thumb is "before" and the right hand thumb is "after".

[strongmanmike]

Hey, imitation is the sincerest form of flattery :love: :cheers:

Yup, came up nicely guys :thumbsup:

Mike

[Stevec35]

Nice one guys. I did this one a few years ago with a different camera. I'm tempted to do it again now.

Cheers

Steve

[markas]

It's a great image:thumbsup::thumbsup: Tremendous detail!

One little niggle - on my colour calibrated screen, the body of the galaxy looks a bit greenish....


Mark

[Atmos]

Just getting better and better :)
It is subtle but an improvement.

[peter_4059]

The Ha certainly makes this galaxy look more appealing. Interesting to see the bright core also.

[Placidus]

Thanks, Mike!



Thanks, Steve. Glad we've inspired you.



A very good observation Mark. I think what happened was the original without H-alpha was relatively well balanced, but because the H-alpha was more topographically discrete, when I averaged the two, the net result was less red, particularly in the areas without special nebulosity. I've reprocessed it under Trish's watchful gaze, stopping short of burning out the H-alpha in an attempt to get the colour balance right. Not as easy as I imagined! The hyperlink should now point to the new, improved colour balance. I've left the old thumbnail. The thumbnail immediately below shows the new colour balance.



Thanks muchly Colin.



Thanks, that's a good point Peter.

Best,
Mike

[gregbradley]

A stunning image, well done.

Greg.

[Placidus]

Thanks for the at-that-moment much needed encouragement, Greg.

Hope you saw the one with the slightly increased red. I was fiddling with the links while you were typing.

Best,
Mike

[Ryderscope]

Definitely worth the extra time to add in the Ha MnT :thumbsup:

[Placidus]

Thanks Rodney! So now we've done several galaxies that look good in H-alpha. From easiest to most difficult, it might be something like:

NGC 300 (amazing and easy to understand what you're looking at because it's face-on)
Barnard's Galaxy (amazing but smaller and fainter)
NGC 55 (easy but harder to see what you're looking at because edge on and tidally disrupted)
Sculptor semi-dwarf (small and faint but you can just make out a micro-quasar !)
Hamburger, where with very long exposures you see the huge faint relativistic jet arching far from the galaxy.

Best,
MnT

[marc4darkskies]

Very nice M&T! I'd personally prefer somewhere between the two versions, but a great rendition nonetheless!

[Paul Haese]

Awesome colour and great close up detail. Huge scale.

[Placidus]

Thanks, Marcus. Somewhere in the multiverse there is now a version with the contrast of the first one and the colour of the second!



Thanks muchly Paul.

Cheers,
MnT

[codemonkey]

Great work guys! I prefer the version with more red.

[Placidus]

Thanks, Lee. I'm Mark persuaded us to try it with more red.

[RickS]

Red is like cowbell... you can't have too much ;) Nice work, M&T. I like the added zing a lot :thumbsup:

[Placidus]

So long as we don't play it in anybody's ear, out of time with the band, or serve with Oeysters. :rofl:

[alpal]

Excellent result Mike & Trish,
I like the final version.


cheers
Allan

[multiweb]

Very nice! I like the redder version. It looks sharper too. :thumbsup:

[Placidus]

Thanks muchly, Allan and Marc.


The discussion about colour has been very helpful. Many thanks to all.

[Andy01]

Me likeum red one too :D

[Placidus]

Thanks, Andy. There's a bit of a consensus developing here! :)

[Ross G]

Hello Mike and Trish.


That is one amazing galaxy photo.


So sharp with excellent detail.


I love the colours in your final version.


Ross.

[Retrograde]

Very nice as always M & T.

Being from the 'too much saturation is barely enough' school myself I prefer the second one :lol: (but both are great).

[Placidus]

Thanks Ross and Pete. Seems the red version wins hands down.

We wanted to be able to say in simple English, and in a package-independent way, where the green tinge came from in the first version, and what we did about it.

We started with a publication-ready RGB, and a publication-ready H-alpha. In version 1, we took the average of the "H-alpha as red", and the red from RGB. That felt right, and worked fine where there was strong H-alpha, but where there was no special nebulosity, averaging the natural red with nothing left a blue-green cast.

In version 2, we simply applied an arcsinh stretch to the red channel from the first version, increasing the red in the non-H-alpha parts by roughly a factor of two, so they came out looking normal again, with no cast. The result was that the H-alpha rich parts came out very strongly red, showing where the H-alpha was, without burning out.

There are a thousand legitimate ways of achieving the same result (natural-looking galaxy where there is no nebulosity, but strong representation of the nebulosity). This way has the advantage of being very easy to explain not just what we did but why it worked, in a package-independent manner.

Best,
MnT