High resolution Cat’s Eye planetary nebula

Image Title: High resolution Cat’s Eye planetary nebula captured in HOO & LRGB using a planetary processing strategy

Copyright: Nicola Beltraminelli & Laurent André

Date image was taken: June 14, 2024

Location: Own remote observatory at E-Eye Extremadura (long exposures)
Vexin, France (short exposures)

Image Description and Details: The project
This is a story of a very friendly collaboration between Laurent, a highly skilled planetary photographer, and a deep sky photographer enjoying processing challenges. The idea was to select a project where our skills and equipment would be most profitable and synergistic to achieve a novel result. We thus selected the very peculiar Cat’s Eye planetary nebula. Astrophotographers are of course aware that planetary nebulas have nothing in common with planets, but for this peculiar object, there is something they share. The Cat’s Eye has an extremely bright core, thus enabling us to capture it with the same technique as for planets! At the same time, the outer shell of the nebula is extremely faint, thus requiring very long exposures to detect it. And finally, of course, one needs to combine the very short exposures with the very long ones and use multiple masks to achieve a representative result that can be visually contemplated. All these elements mixed generated a fantastic and exciting cocktail of technical and processing challenges (and this is an understatement!).
To achieve the above, we applied the following strategy:
Laurent generated ~500'000 (!) images of 200 and 250ms in L and RGB with his C14 edge HD scope at both the native focal length of 3910mm, as well as coupled to a Powermate x2.5 pushing the instrument to a 9750mm effective focal length to resolve the core. He then integrated ~20'000 images of L at 9750mm and ~14'000 images of RGB (color camera) at 3910mm. He also used his C11 scope to obtain a series of Ha and OIII images of the inner and outer shell with exposures of 180s and 600s. From my end, I generated LRGB images at 600s with my SVX180T lens to capture the stars, galaxies and the outer Cat’s Eye shell. The 200/250ms exposures were processed by Laurent using planetary techniques, whereas I took care to process the long exposures with PI and PS. The final composition was processed by combining our skills and points of view.

The final composition
Upon completion of the processing of the core and outer shell, we decided to generate an image showing the full nebula in HOO and to include the core, the stars and galaxies in LRGB. To obtain a more representative vision of the whole nebula, we maintained a near to saturation version of the core, which is extremely bright as compared to the extremely dim regions of the shell. As the core was processed with a planetary imaging technique, we decided to include a magnified version of the core obtained from the 9750mm data, and we adapted the luminosity to better illustrate the colors and contrast nuances.
To our knowledge, this processing scheme enabled us to obtain an unprecedented level of details of the core with non-professional material, and at the same time to show the rings and their structures, as well as the outer shell.
According to our rough estimate, the level of details observed in the core of our image is around 0.3 arcsec, which is of course inferior to what can be achieved on planets such as Jupiter, but considerably superior to classical deep sky astrophotography.

For the outer halo & nebula surrounding
Astronomik H-alpha 6nm: 140×180″(7h)
Astronomik H-alpha 6nm: 138×600″(23h)
Astronomik OIII 6nm: 55×180″(2h 45′)
Astronomik OIII 6nm: 61×600″(10h 10′)
Chroma Blue: 30×600″(5h)
Chroma Green 50 mm: 30×600″(5h)
Chroma Red 50 mm: 30×600″(5h)
Chroma Clear 50 mm: 71×600″(11h 50′)
For the core:
Integrated Subs with ASI462MM : 10000×0.2″(33′ 20″)
Integrated subs with ZWO ASI585MC: 34000×0.25″(2h 21′ 40″)

Equipment Details: For the outer halo & nebula surrounding
Scopes: SVX180T, C11 Edge HD
Mounts: 10 Micron GM2000 HPSII ; 10Micron GM1000 HPS
Camera : ASI6200MM

For the core
Scope: C14 Edge HD
Cameras: ZWO ASI462MM; ZWO ASI585MC (no filters)
Mount: 10Micron GM1000 HPS