Planewave CDK12.5; AP 1100GTO AE; ASI6200MM, - Antlia Pro Broadband and 3.5nm Ha filters
SHO: (34,41,34 x 420s, Bin 1, Gain 200) (representing appox 50% of total frames taken)
Total integration time = 12.7 hrs (Apr 16,17,18,19,21  2024)

M57 is a popular target in both narrowband and broadband imaging, due to it brightness and colourful emissions.   In RGB broadband, it appears as and of red and white, with a dimmer central blue core.  This ring of red and white is the brightest part of the PN, and the source of it’s common name – the Ring Nebula. 

When imaged in narrowband, however, the complex shape of this planetary nebula becomes evident.  The bright ring takes on the more complex shape of a helix or spiral that we are looking down the barrel of from our perspective.  Its colour appears white (strong S,H and O signals nearer the nebulas centre), but a mixture of yellow (H) and red (S) dominated signals as the O signal declines.

From a narrowband perspection, a more appropriate name for the PN might have been the “Onion” Nebula, as two additional layers become evident with sufficient integration time.   Outside of the ring, a florette patterned layer of blue O signal forms another layer of this onion, followed by a patchwork of yellow/green/red strong H, and to a lesser extent, S signal furtherest out.    Notably, this outermost onion layer forms an almost perfect circle, suggesting that it may be spherical in nature, in stark contrast to the ring/helical spiral.  

Thank goodness that our intuitive belief that exploding stars should generally result in a spherically symmetric patterns remains intact.  At the same time, spins, asymmetrical material and radiation distributions, magnetic moments, and prevailing winds can make planetary nebulae take on a wide variety of forms.

For some reason (red shift?), the nearby galaxy IC 1296, along with even fainter galaxies, appeared strongest in S signal and thus red in the image.  The star colours, on the other hand, were obtained through a combination of narrowband signals to mimic broadband colours and forced calibration to the true stellar spectra.   

Almost 50% of the total frames taken were culled due to mixed sky conditions and my desire to use only the best frames to emphasize all of the dim layers of this onion.[color=var(--lighterGrey)] [/color]