The Helix Nebula (NGC 7293) is our nearest planetary nebula located about 700 light-years from Earth in the constellation Aquarius. It formed when its central star shed its outer layers as it nears the end of its life, ultimately fated to become a white dwarf. One of the unique features of this planetary nebula is the comet like features (cometary knots) that point towards the central star with tails pointing away. These cometary knots are thought to be formed when winds outflowing from the central star encounter globules of material in the shells blown out from the dying star.
The Helix Nebula is a target that I have long wanted to image but I never managed to get the timing right. From southern Arizona, it is very low on the horizon providing very little time above 30 deg in altitude. In past years, the weather has not cooperated when the timing was right. Luckily 2023 was different.
I took data in all my available channels: R, G, B, Ha, SII, OIII but I wasn't really sure how to process all of this data together. As I really liked the RGB colors, I wanted these to drive the image. Ultimately, I never came up with a satisfactory solution, so I created a super luminance image from all of my data and used it to colorize the RGB data. In the future, I may process the narrowband data by itself.
My goal for this image was to reveal some of the cometary knots. To this end I did two critical things:
- I used drizzle integration to double the resolution (I was slightly under sampled given my seeing). This image is a crop of my system's FOV.
- I spent a lot of time learning to use the PixInsight GeneralizedHyperbolicStretch feature to maximize the contrast in the central disk and first ring of the nebula
I feel I achieved my goal but the low position of the Helix in my southern skies definitely limited what I can do with this subject.
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