A Deep and Dusty Cocoon

Mike Lewis

Mike Lewis

Staff Member
The Cocoon Nebula (IC-5146) is portrayed here in a wider FOV, showing the extensive dust and glowing gas in the region surrounding the actual nebula itself. This is a natural color RGB image with Hα data added to bring out the extensive dim clouds of ionized Hydrogen in the area surrounding the nebula.

The Cocoon Nebula is thought to be approximately 4,000 light years distant in the Cygnus region of the sky, and is composed of both emission and some small reflection areas of nebulosity.

This was a real challenge to process, and I actually ended up NOT using an additional ~2 hours of luminance data because I could not get it to combine in a way I liked. In retrospect this might have benefited from 10 min RGB subs as well, since the dust components are really quite faint compared to the brighter nebula itself. But I think I ended up with something that shows off the complexity of the region around the nebula which was what attracted me to the target in the first place.

As always comments and critiques most welcome, and thanks for looking!

LRCC_sRGB_FW_UTIFF_V2_CocoonSVQ100_HaRGB_AdvSharp_PSCC_WithStars_LHE.jpg



Equipment:
QHY268M Camera @ -5C and
Gain:56 Offset:20 / Gain:0 Offset 20
Software Bisque MyT Mount
Stellarvue SVQ100 Astrograph Refractor, 580mm @ f/5.8
Antlia Pro Filters (3nm narrowband plus LRGB)
QHY OAG-M/ASI290MM

Software:
Pixinsight Commercial Version 1.8
Lightroom CC
Photoshop CC
N.I.N.A. Control Software
BlurXTerminator (Russell Croman)
StarXTerminator (Russell Croman)
NoiseXTerminator (Russell Croman)

Light Frames:
Gain 56 / Offset 20
Ha: 58 x 600 secs (9 hrs 40 mins)

Gain 0 / Offset 20
Red: 12 x 30 secs 6 mins)
Green: 11 x 30 secs (5 mins 30 secs)
Blue: 11 x 30 secs (5 mins 30 secs)

Red: 65 x 300 secs (5 hours 25 mins)
Green: 66 x 300 secs (5 hours 30 mins)
Blue: 61 x 300 secs (5 hours 5 mins)

25 hrs 57 mins total

Dark Frames:
10 x 30 secs (5 mins)
10 x 300 secs (30 mins)
10 x 600 secs (1 hr 40 mins)
 
JimFox

JimFox

Moderator
Staff member
Hey Mike,

You sure got a lot of surrounding Ha data around the Cocoon.

I like your detail on the Cocoon itself. But I think the background has lost something. The stars don't look right, but they are like colored over and seem muted. The red Ha background area feels flat if you will. Something doesn't feel right. Almost like the Cocoon is in 32bit data but the background nebulosity is in 8 bit. (I know it's all 8 bit here)
 
Mike Lewis

Mike Lewis

Staff Member
JimFox said:
Hey Mike,

You sure got a lot of surrounding Ha data around the Cocoon.

I like your detail on the Cocoon itself. But I think the background has lost something. The stars don't look right, but they are like colored over and seem muted. The red Ha background area feels flat if you will. Something doesn't feel right. Almost like the Cocoon is in 32bit data but the background nebulosity is in 8 bit. (I know it's all 8 bit here)
Click to expand...
Good feedback. I spent a lot of time trying to combine the Hα and the RGB. This is my favorite version, but it is certainly not the only result. I think that the Hα data, being composed of 10 minute subs at higher gain, is 'deeper' than what I got in the RGB data, even though that was a combination totalling 16 hours versus the ~10 hours of Hα data. If I had it to do over again, I would have tried the longer subs for the RGB and/or run those channels at the same gain (56, which corresponds to 100 on the ZWO equivalent camera, right at the dual gain noise reduction point). No way to know if that would have helped, but I was after the dust and I am sure the RGB is stretched 'harder' than the narrowband data in this case to try to bring that out...

As for the stars, they were also at low gain and only 17 mins of total integration. I have done that before and liked the results. In this case though, perhaps too little data, making the stars almost too small. I do like the star colors, but once again could probably benefited from either longer exposures or higher gain for the stars too. All comes back to the feeling that I still ironically have a MUCH easier time processing full narrowband data than I do RGB data these days :)

I was dealing with some strange tracking issues that I think I have figured out after the fact were due to the way NINA was handling focusing after filter changes, so I ended up throwing out almost 5 hours of data due to bad star shapes. That certainly didn't help things either. Hopefully when I am able to next collect data, I can tweak a few settings in NINA and fix that issue at least.

ML
 
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