Greetings All,
We've had a lot of Helix nebula pics contributed to the forum of late, so here is my rendition of
NGC 7293 – The Helix Nebula.
The Helix Nebula (NGC 7293) resides in the constellation Aquarius and is dubbed the “Eye of God”. It is one of the closest of all planetary nebula at a distance of approximately 450 light years and is about half the size of a full moon. Despite its size, the light is spread over a large area making it a difficult object for visual observation. The nebula displays different ionisation levels of ejected matter from the dying central star. The inner blue hue indicates the presence of excited oxygen atoms, while the vibrant outer structure consists of hydrogen and nitrogen atoms.
About the image;
The image is a [LHa]RGB composite with a total exposure time of 4.5 hours (L:60min,Ha:60min,R:50min,B:50min,G :50min). The Luminance and Ha data I combined was really weak/crap. I’m not overly pleased with the resolution obtained. Two hours should have been sufficient to bring out the cometary knots. It also didn’t help that I collected the luminance data when the object was relatively low. May revisit another time to collect better luminance data. My imaging goal for this target was to not just too bring out the show piece object, but also lift the image to display its environment. I kept this in mind with processing the data and made subtle tweaks to emphasis features of interest in particular background galaxies. I actually prefer this target in narrowband compared to RGB as the mapped colours really gives an extra dimension/wow factor. In my opinion, RGB appears a little flat. For the record, colour balance is slightly out. The inner shell should have a greenish tint. I attribute this to either lack of RGB data (likely cause) and/or the Astrodon filters are not true 1:1:1 ratios, but 1:1.2:1.2 for the specific imaging set up. May need to perform some G2V tests to confirm.
Image Processing;
The typical dark/flat/bias calibration. Registered in Registar. RGB was 2x2 bin, thus scaled to luminance (1x1). Median combined in MaximDL. Data was extremely noisy so plenty of image cleaning performed. Hot and dead pixel removal performed using the RC Console in MaximDL. A few major gradients to deal with, one of which took some time to process out. Primarily worked in MaximDL to remove these. Lum and Ha blended in PS using lighten mode. Shadow/Highlights tool used for non linear chrominance stretch. I blended the luminance data in twice to obtain better control over colour saturation (first at 40%, the second at 100%). Minor noise reduction, though think I could have gone harder as the data is still noisy.
Thanks for looking, hope you enjoy.
Cheers
