Happy Valentine's Day! ❤️
Thought it appropriate timing to publish my first complete image of IC1805 - The Heart Nebula and its neighbour IC1848 The Soul Nebula, which I did as a surprise commission for Valentine's Day for my wife.
I've struggled to capture the nebulosity of this on my mono ZWO ASI1600MM, so switched to the newer ZWO ASI2600MC-DUO combined with a RedCat 51 and had much more luck. That plus a few freezing cold nights of clear skies gave me enough time to capture some clear data.
As ever I am climbing the cliff-face of a learning curve with PixInsight and improving my process, which I've documented below:
- Weighted Batch Pre-Processing with 2x drizzle to solve for under-sampling.
- Resample so the image is a suitable size to process further.
- Image Solver to repair the solution after a resample.
- Spectrophotometric Colour Calibration.
- Dynamic Background Extraction using VisibleDark's 'lazy' method. I tried AutoDBE here but as there's a bunch of faint nebulosity between the targets I needed to nuke, it was making the image 'soupy'.
- NoiseXTerminator.
- StarXTerminator and kept the stars for re-adding at the end.
- SCNR to remove any green cast.
- Stretch to non-linear using Generalised Hyperbolic Stretch. This is a new one for me and recommended on the Stargazer's Lounge forums as much more robust than the normal Histogram Stretch. It looks daunting at first but this Adam Block tutorial is fantastic for making it make sense, including the theory.
- Masked the two nebula and a further stretch to dim the background.
- Unsharp mask to bring out the details.
- Even after all that work I had a weird blob of light in one corner of the image that was distracting the eye from the centre of the target. I couldn't stretch or curve it out as it was impacting the image, so I learned how to do a feathered circular mask to mask the entire image except for that top left corner, then used Histogram Transform to crush out the colour entirely. I learned how to do this here, where they use it with processing solar photos to protect the Sun.
- Stretched the stars to reduce them in number and intensity.
- PixelMath to recombine the stars to the base image: ~((~Starless)*(~Stars)).
Special thanks to the contributors on Stargazer's Lounge who gave some great feedback and suggested a few of the tools in the process above. You can see the evolution of this picture
here.
Comments