NGC6543 - Cat's Eye Nebula - SHO (Hubble Pal) - Jun 2022
Planewave CDK 12.5 - AIS6200MM
A-P 1100 GTO AE, Antlia Pro 3nm NB filters
HSO (3 x 16 x 300s exposures) = 4 hours, Bin2x2, Gain=200!
Although it looks nothing like the images you see from the HST, This is the same "Cat"s Eye" Planetary Nebula or NGC6543. The dying star at the centre of the nubula is anomalous for white dwarf stars, in that is pulsates every 1500 years, ejecting a fresh about of matter each time. The result is a set of "onion layers" emanating out from the centre.
The structure of the very bright centre of NGC6543 is captured beautifully by the Hubble telescope, but is too small for my gear to get anything more than a hint of it. However the narrow band filters capture a much large "shell" of O+2 emissions surrounding the core that appears visually like a mini super-nova remnant. A good thing, otherwise this would be a boring subject.
This was a very difficult image to process, due mainly the huge contrast between the nebula core and the outer halo-shell. Just about every process I touched ruined the image (reverse Midal touch) , so what you see here is just false colour manipulation, stretching (GHS to retain core details), and noise reduction. It was difficult to capture the outer shell while avoiding overexposing the inner core with every process wanted to identify the core as a star. The core is so bright it created its own large diffraction spikes.
The other difficulty is the complete dominance of the oxygen (blue) signal over both hydrogen and sulfur.
This image marks the "end" of the clear sky drought here, and fear that it was a one off, led me to operate my camera at Gain 200 (0.1 e-/ADU) for the first time. It was a lot noisier than Gan 100, but at least I was able to get enough frames in one night to make a half-decent image. Feast or famine though, as I now have a backlog of processing thanks to several clearish nights in a row.
Any hints on better processing techniques are most welcome.