Hi All,
With the clouds slowly parting as the monsoon season draws to a close, I’ve managed to acquire a quick set of data to complete another image. So, without further delay, I’m pleased to present
IC5146 – The Cocoon Nebula
About the target;
The Cocoon Nebula (IC5146) is located in the constellation Cygnus and resides 4,000 light years away. This remarkable nebula is intriguing in that it has emission, reflection and absorption characteristics due to dust particles in the region. The nebula is also a stellar nursery harbouring an open star cluster containing approximately 80 young stars in which some can be partly seen through the folds of nebulosity.
About the image;
The image is an [Ha+L]+LRGB composite consisting of 2.5 hours total (Ha:60min,RGB:30min respectively) taken from the
Lightbuckets 24” RC (4876mm F/8), Rodeo – New Mexico. Four data sets were created: synthetic lum which was created from the RGB filtered images as I didn’t collect any luminance data on the rig, Ha, RGB ( w/ratio of 1.11:1.0:1.04) and a DDP stretch (hard stretched) RGB. Ha and lum placed through two iterations of deconvolution to handle the oversampling (.57 arcsec/pixel) and generally tighten the image. I created the synthetic lum to manage the Ha data integration considering the Ha data has very tight small stars, it’s difficult to match broadband filtered data. The synthetic luminance was blended in as lighten mode on top of the Ha layer in PS. Subtle adjustments were made to the opacity to bring it together. Not a huge amount of RGB data given the total integrated exposure times which made stretch the data hard. The synthetic luminance on the other hand was fine as I didn’t need to stretch the data too hard to being out the stellar profiles. The RGB data was put through neat image using layer masks to keep stars intact, but controlling noise. I found it complex to integrate the Ha data into the RGB. In most cases I’d blend 10% or so into the red channel, but the Cocoon is different target, one of which I’ve never handled before. As its part reflection, part emission, integration of Ha+R dominates the image. So I took a different approach by progressively blending the Ha data into the synthetic luminance. This process was performed three times, each time opacity was increased along with saturation so I could monitor both histogram and general aesthetics. I do however feel I lost some of the blue reflection nebulosity in the process. To circumvent this, I introduced another layer being the DDP stretched RGB. This layer was stretched rather hard, almost to the point of clipping, then heavily boosted in colour saturation. At the top of layer stack it was integrated as a soft light blend. As soft light is a darkening function, its important the data is stretched reasonably hard. I then altered the opacity looking for any form of data clipping in the RGB channels. – none present. Subtle selective contrast masking was performed to bring out the highlights and darken specific features, followed by minor colour balance tweaks to the shadows. Seasoned to taste. Don’t feel I managed the stars very well, but it works. A few internal reflection problems with the green filter due to a bright star off the edge of frame. I desaturated the area, but was not enthusiastic about chasing it due to a possible upset of the dusty regions.
Anyway until next time, Enjoy!
Cheers