The Crab Nebula is a very renown supernova remnant and pulsar wind nebula in the constellation of Taurus. The common name comes from a drawing that somewhat resembled a crab with arms produced by William Parsons, 3rd Earl of Rosse, in 1842 or 1843 using a 91 cm telescope. The nebula was discovered by English astronomer John Bevis in 1731. It corresponds with a bright supernova recorded by Chinese astronomers in 1054 as a guest star. The nebula was the first astronomical object identified that corresponds with a historically-observed supernova explosion (source Wikipedia).

The objective of this project was to obtain a detailed version of M1 by taking advantage from one end of the narrow band filters to show the emission filaments of the nebula, and from the other to use the total light to illustrate the entire nebula. As a matter of fact, although the filaments shown by the narrow band filter enable to appreciate the beautiful gas complexity, the core brightness is predominantly emitting at all wavelengths. From my perspective cutting the light from the core impairs the representativity of what this nebula contains. I therefore tried to combine layers from Ha, SII and OIII emissions, as well as from total light, that I used as luminance layer at 80%. Using this combination I noticed that the nebula achieved a better 3D impression with slightly less sharp filaments than with a pure SHO version.

To maximize the resolution I kept only the raw images with the best HFR values. Down to practice I rejected >70% Ha images (very unstable nights...), 30% of SII, 30% of OIII and 20% of L subs. During the pre-processing I drizzled all the stacks 2-fold. The objective was not to gain details, but to enable an easier appreciation at 100%. I applied BXT 070 for sharpening and Denoised exclusively the S, H, O layers (not the L).

About the processing, conversely to the usual practice, I associated Red to Ha, Green to SII and blue to OIII. I equilibrated the colors with the "selective color funtion" in PS. The stars were calibrated with SPCC.

As usual don't hesitate to provide constructive feedback for a continous improvement.

CS!

Nicola