Cocoon close up

[alan4908]

The Cocoon Nebula (IC5146) is located in Cygnus and is both a reflection and emission nebula.  It's about 4000 light years away and spans 15 light years. The emission nebula, consisting of glowing hydrogen gas appears red whilst the reflection nebula appears blue.  It also contains an open cluster of young stars which includes the bright star seen at the centre of the nebula, below. 

This LRGB image image has an Ha blend into the red channel and was taken with my Esprit 150. It represents an integration time of about 27 hours.

I hope you like it !

Alan 

 

LIGHTS:  L:13, R:13, G:12,B:9, x 600s Ha: 39 x 1800s. DARKS: 30, FLATS:40, BIAS:100 all at -20C.

[Dark Horizon]

Nice image. However i much prefer this with a lot more space around it, there's so much more to this target. Great pic all the same

 

[alan4908]

12 hours ago, Dark Horizon said:

Nice image. However i much prefer this with a lot more space around it, there's so much more to this target. Great pic all the same

Thanks for the comment.

Yes, I agree that there's quite a bit going on around this nebula, here, I was interested in gathering details - if you want to see a more wide-field shot have a look in my album Deep Space Sky II which contains images from my SW ED80.  Maybe I should try to combine the two images with Registar 

Alan

[Rodd]

I think you can back off the stretch a bit--image is very bright and stars look like they are a bit bloated.  I think if you dim the histogram a bit the details will pop even more.  Nice close up

Rodd

[carastro]

I like it,

I think this target looks good both as a close and as a wider field which shows the dark Nebula but then you lose the detail in the cocoon.

I found when I cropped my image I got large stars too.

Carole 

 

 

[alan4908]

4 hours ago, Rodd said:

I think you can back off the stretch a bit--image is very bright and stars look like they are a bit bloated.  I think if you dim the histogram a bit the details will pop even more.  Nice close up

Rodd

Thanks for the comment Rodd. 

Yes, I agree the image is bright but I quite like this level which is primarily to highlight the gaseous white parts of the nebula. If you hover around the image you will find that parts of it are actually very dark. 

I agree that some of the stars are large but since they are are bright and the image is cropped, I personally think that is OK - but again thanks very much for your comment  

2 hours ago, carastro said:

I like it,

I think this target looks good both as a close and as a wider field which shows the dark Nebula but then you lose the detail in the cocoon.

I found when I cropped my image I got large stars too.

Carole 

Thanks Carole - I think I am coming the conclusion that I am more of a details man. 

Alan

[alan4908]

I decided to try out some star manipulation techniques with the objective of making the Cocoon stand out a little more from the star field.  For those who may be interested I used:

1. A PI circular Kernal erosion filter on the bright stars.

2.  A PI star de-emphasis technique on the lower/medium bright stars. 

3. A PS radial blur on any wonky stars.  

Alan

[ollypenrice]

I like the nebula very much.  The little blue nebula is very reclusive but you have it!

I'm less keen on the noise reduction around the main nebula. Some was doubtless necessary but I always feel that, when you can see it, it's too much.

Olly

[alan4908]

19 hours ago, ollypenrice said:

I like the nebula very much.  The little blue nebula is very reclusive but you have it!

I'm less keen on the noise reduction around the main nebula. Some was doubtless necessary but I always feel that, when you can see it, it's too much.

Thanks for the comment Olly. 

I'll  go back to my processing to see if I've overdone something on the noise reduction front. I have to say that I find noise reduction very challenging to get good results. Currently, I'm hoping between Pixinsight, PS and NeatImage.......

Alan

[alan potts]

A lovely image indeed, must have try for this one , and if half as good I will be happy.

[ollypenrice]

17 minutes ago, alan4908 said:

Thanks for the comment Olly. 

I'll  go back to my processing to see if I've overdone something on the noise reduction front. I have to say that I find noise reduction very challenging to get good results. Currently, I'm hoping between Pixinsight, PS and NeatImage.......

Alan

I don't think the algorithm chosen is very important, it's how far it's applied and where. For me Photoshop is perfect for the job because you can use layers rather than masks and then easily and quickly select the parts to be noise reduced with the opacity slider there to decide on the extent. I would make a copy layer and apply very slightly excessive NR globally to the bottom layer. Then, on the top layer, I'd use the colour select tool to choose the noisiest parts and run a partially opaque eraser over the selection. I might then expand the selection, reduce the opacity of the eraser and apply it again. This way you can see what you're doing as you do it.

Olly

[alan4908]

23 minutes ago, ollypenrice said:

I don't think the algorithm chosen is very important, it's how far it's applied and where. For me Photoshop is perfect for the job because you can use layers rather than masks and then easily and quickly select the parts to be noise reduced with the opacity slider there to decide on the extent. I would make a copy layer and apply very slightly excessive NR globally to the bottom layer. Then, on the top layer, I'd use the colour select tool to choose the noisiest parts and run a partially opaque eraser over the selection. I might then expand the selection, reduce the opacity of the eraser and apply it again. This way you can see what you're doing as you do it.

Olly

Many thanks for the tip Olly - I don't use the technique you describe but I shall give it a go.

One final thing, would you mind indicating which parts of the nebula you believe have excessive noise reduction. I compared my image with a Adam Block reference ( http://www.caelumobservatory.com/gallery/ic5146.shtml)  and I cannot see the issue. 

Alan

[alan4908]

1 hour ago, alan potts said:

A lovely image indeed, must have try for this one , and if half as good I will be happy.

Thanks Alan 

Edited August 2, 2019 by alan4908

[ollypenrice]

1 hour ago, alan4908 said:

Many thanks for the tip Olly - I don't use the technique you describe but I shall give it a go.

One final thing, would you mind indicating which parts of the nebula you believe have excessive noise reduction. I compared my image with a Adam Block reference ( http://www.caelumobservatory.com/gallery/ic5146.shtml)  and I cannot see the issue. 

Alan

I feel I can see pixel to pixel smoothing in the dark signal of the areas indicated here but most clearly in the upper left.

I've heard this described as the 'vaseline on the lens' look which creates a fairly large scale mottle while removing all grain. Compare that with the grey-ish outer shell of your nebula. While I dare say you've applied some NR to this it still has a fine surface grain which I feel keeps it natural looking. 

The dark regions in Adam Block's image are incredibly smooth but don't have the tell-tale larger scale mottle arising from NR. He probably got the smoothness from vast amounts of signal but, being strictly honest, I do suspect a little too much NR for my taste even in his. (And I think his processing is masterful, let's be clear about that.) I've been accused of over-zealous NR when I hadn't used any at all, just extremely long exposures, so I don't want to make the same accusation against Adam Block!

I think the way to get your eye in on the effects of NR is to make a set of copy images and apply increasing amounts of NR to them, starting with not enough and ending with excess. This will let you see just what to look out for in terms of negative consequences. Also NR is far less obtrusive when it is applied only to the dark signal and is punctuated by fully sharp contrasting features. That's why the Colour Select tool is so powerful.

For what it's worth I'll be posting a Cocoon on here shortly but it's on Astrobin already: https://www.astrobin.com/418330/

Olly

 

[alan4908]

Olly

Many thanks for the explanation. I must admit that I cannot see an issue in the areas you've marked on the posted image. However, when I zoomed in on the TIFF I can definitely see what I would describe as a soft focus effect in parts of the image.  So if I zoom in on the fours corners and centre of the image I get this:

 

If you look at the stars, the top left is most soft focus with the centre being the most sharp.  Now that I can see this,  I shall now explore where this came from.  

Alan

Edited August 2, 2019 by alan4908

[MarsG76]

Thats close.. very smooth.. perhaps the NR is a bit heavy but the detail is still there.

 

[alan4908]

1 hour ago, MarsG76 said:

Thats close.. very smooth.. perhaps the NR is a bit heavy but the detail is still there.

Thanks 

Alan

[alan4908]

3 hours ago, ollypenrice said:

I've heard this described as the 'vaseline on the lens' look which creates a fairly large scale mottle while removing all grain. Compare that with the grey-ish outer shell of your nebula. While I dare say you've applied some NR to this it still has a fine surface grain which I feel keeps it natural looking. 

Hi Olly

Just to let you know that I've found the root cause - a little too strong application of Pixinsight's TGV Denoise. As I previously mentioned,  I can see the effect when I zoom in but in posted image I cannot, which is why I missed this whilst processing. 

Many thanks again for your critique, hopefully this will allow me to improve. 

Alan