Sh2-155 (Cave Nebula) (Ha)SHO

[Rodd]

Not sure the "Cave Nebula"  is the most suitable name for this very interesting DSO. 

Televue np101is with .8x reducer, SBIG STT-8300 with Astrodon 3nm filters

18 Hours of exposure 6 each in Ha, OIII, and SII in 30 minute subs (36 subs)

2 versions attached.  There many versions of this image, and with  numerous forks in the road of processing, It is sometimes difficult to decide which fork to choose.  Before I move on and try to produce  a finished product, I am faced with this fork:

1) after using the  Magenta Star Reduction script with no star mask

2) After using the magenta star reduction script with a star mask

It seems to me that the Magenta star reduction script left  the image with a slight green tint that I am not sure I like. But I am not sure I don't prefer it either. The other image, with the use of the script  with a star mask is nice--but a couple stars have the halo, and it has a violet cast, which I am not sure is better than the other.  SCNR  does not solve the issue.  So.....short of being able to isolate the halos and apply the script (currently beyond my abilities), which version is....more appealing?

 

[astro mick]

What a superb image Rodd, beautifully processed.

Amazing.

Mick.

[Rodd]

4 minutes ago, astro mick said:

What a superb image Rodd, beautifully processed.

Amazing.

Mick.

Thanks Mick.

[PatrickGilliland]

Thats very nice Rodd - prefer V1 think the palette is excellent and unique, thumbs up here.

Paddy

[Davey-T]

Good work Rodd, I prefer the second version with magenta stars ala Hubble, though either stands up well.

Dave

[Rodd]

24 minutes ago, PatrickGilliland said:

Thats very nice Rodd - prefer V1 think the palette is excellent and unique, thumbs up here.

Paddy

 

11 minutes ago, Davey-T said:

Good work Rodd, I prefer the second version with magenta stars ala Hubble, though either stands up well.

Dave

Thanks Guys......still on the fence.  

[Rodd]

I like the way the images look until enlarged and under zoom--then the shortcomings of noise reduction raise their ugly heads.  here's another effort, with a different approach to noise reduction. (more early, less late).  Still not satisfied.  Now I must go through the unenviable task of hunting down the specific causes of image degradation.  What causes the granulation of the outlying areas?  Maybe the background is stretched to hard.  Back to the drawing board!

[Rodd]

Well--Here is my final version for now--much less aggressive with my stretches and noise reduction.  The magenta star reduction script did not effect anything but the stars--which are slightly bigger, but better overall I think.

[Rodd]

Here is the same I'm age with a bit smoother background--final tweak on noise Reduction

[Rodd]

I forgot the last step--here it is.  Sharper details in core.  Now I am done with this version.  Again--not bad at a 1:1scale, maybe 1:2--but full image zoomed it breaks down.

 

 

[Rodd]

This is the same data processed using a workflow I was taught.  I think it is better, but I am still not satisfied with the extremities.  They all might look fairly decent when they are small.  But when they are opened, they are quickly closed.

 

[ultranova]

very nice indeed, the first two are to me the best out the lot, they

don't look to over processed and stand up better at 100%,

The last image looks like it has to much contrast and over sharpening

But beauty is in the eye of the beholder,

Otherwise a great take on the cave nebula

Well done

Paul

[Rodd]

Thanks--but I had a go again and I finally think I see some improvement.  Clouds seem a bit more realistic to me.  And the background is not blue. Holds up better at full size.

 

 

[Rodd]

Finally, a version showing signs of promise.  Been a long hard climb.  One of these has more noise control--not sure if its too much so I posted both.

 

 

[ollypenrice]

A most original rendition. I like it a lot. I think the 'Cave' name arises from its appearance in broadband more than in emission, though even then it always strikes me as a bit tenuous!

Olly

[Rodd]

7 hours ago, ollypenrice said:

A most original rendition. I like it a lot. I think the 'Cave' name arises from its appearance in broadband more than in emission, though even then it always strikes me as a bit tenuous!

Olly

Olly--I am very gratified that you like it, though the fact that it is a "most original" rendition concerns me, as I did nothing different or "original;" with the data.  I simply combined equal amounts of Ha, OIII and SII into what is commonly referred to as the Hubble Pallete, and did the same basic processing steps that are done for all images (about 1,000 times!)  I am aware that the image looks quite different than most that I have seen......and that is what concerns me.  It shouldn't.  Trying to get to the bottom of that has been frustrating.

[Davey-T]

Prefer these latest versions Rodd, more my idea of the Hubble palette, even retained a faint bit of magenta in the stars.

Dave

[ollypenrice]

1 hour ago, Rodd said:

Olly--I am very gratified that you like it, though the fact that it is a "most original" rendition concerns me, as I did nothing different or "original;" with the data.  I simply combined equal amounts of Ha, OIII and SII into what is commonly referred to as the Hubble Pallete, and did the same basic processing steps that are done for all images (about 1,000 times!)  I am aware that the image looks quite different than most that I have seen......and that is what concerns me.  It shouldn't.  Trying to get to the bottom of that has been frustrating.

My friend and frequent collaborator, Tom O'Donoghue, who is the best widefield astrophographer in the world so far as I'm concerned, has a saying: Make your own picture.

I liked the neutral charcoal grey-blacks in your image and I think that they are particularly important in an object which is as much about dusty obscuration as about emission.

Olly

[Rodd]

53 minutes ago, Davey-T said:

Prefer these latest versions Rodd, more my idea of the Hubble palette, even retained a faint bit of magenta in the stars.

Dave

Thanks Dave--So often have I deluded myself into thinking I improved the image.  Its nice to have that come to fruition for a change.

[Rodd]

26 minutes ago, ollypenrice said:

My friend and frequent collaborator, Tom O'Donoghue, who is the best widefield astrophographer in the world so far as I'm concerned, has a saying: Make your own picture.

I liked the neutral charcoal grey-blacks in your image and I think that they are particularly important in an object which is as much about dusty obscuration as about emission.

Olly

I guess the real question is "am I done?"  For now I have to be, for if I work on this image any more at this time I will implode.  But I find that images can look very nice small--but when opened in "full Image" mode, they look terrible.  Also, I have a 4K screen that I process on and images can look staggeringly good on that, but terrible on my desktop screen which is much lower resolution.   As Dave indicated, I think the last 2 images are much better than the impervious dozen---but I am not convinced they look "right".

Rodd

[johnrt]

Those last 2 are head and shoulders above the rest Rodd. Well done.

[Rodd]

34 minutes ago, johnrt said:

Those last 2 are head and shoulders above the rest Rodd. Well done.

Thanks Johnrt