Planetary Nebula (NGC7008) in RGB (Cygnus) - June6,7,8 2023
Planewave CDK12.5 - ASI6200MM
A-P 1100 AE GTO, Antlia Pro BB and 3nm NB filters
R,G,B: (15, 15, 15 x 150s exposures, Bin 1x1, Gain 100)
H,O: (35,29 x 600s exposures, Bin 1x1, Gain 100)
Broadband Integration TIme = 1.9 hrs; Narrowband Integration Time = 10.7hrs
Total Integration Time = 12.5 hours
NGC7008 is a Planetary Nebula and is another great offering by Cygnus. A planetary nebula forms during the death of a medium sized star and is the likely destiny of our own sun. Once such as star exhausts its fusion fuel, it can no longer balance its volume against gravity and collapses. The star material changes is state from hot plasma to something where the atoms are packed much more closely together - so much so that what would have been a star much the same size as the sun is reduced to the size of the earth - hence the names: "dwarf star" to the star and "planetary nebula" to the star and surrounding gasses.
Electrons in their probability orbitals in the atoms of a "white dwarf star" are pushed into their lower (smaller) energy state and material gains kinetic energy as it falls rapidly toward the centre and consequently a burst of energy is released when the collapse occurs, that we call a nova. While most of the star is collapsing, this energy blows away some of the material within the star itself, forming a cloud around the white dwarf. With still more energy to get rid of, the white dwarf also emits intense UV radiation that energizes the cloud which in turn emits visible light in colours associated with its makeup.
The cloud can be as bright as surrounding stars. Unfortunately, they are very small and generally larger focal lengths are required.
This RGB image was captured in less than 2 hours of imaging time (including rejected frames). The Planetary Nebula is known as the "Fetus Nebula", and it does resemble either a (maybe ultra-sound false colour?) image of a Fetus.
In this image you can "see" both the cloud and the remaining white dwarf star.
My initial goal with this target was to capture it in narrowband, both for its own sake and to provide me with some practice for a more ambitious project). It is interesting to compare the result with that achieved with the only broadband RGB filters and less than 20% of the total integration time.  Both images were oversampled at 0.3"/pixel - just because the target is small and I don't think it ultimately hurst.
First off, the stars in this image are dimmer and than the RGB version. The stars from the Ha filter were used, which I often do to help keep the stars from obscuring the nebulosity. As a result, some stars are actually missing in this image, most notably some tiny stars that are right on top of the nebula (PN) itself.
The wavelength selectivity and increased exposure time with the narrowband filters did enhance the ability to draw out both more (the dimmer parts of the PN) and the details of the overlapping "shells" of material surrounding the dwarf star. I think the HO rendition may be technically superior (reveals more information) about the PN, but the RGB rendition does look more like its namesake "Fetus", and retains an more mysterious aura.
I am fairly pleased with the false colouring technique used on the nebula, and it almost mimics that of RGB. Note the star colour in both version used RGB colour information, though.
Which one's better? I think it depends on the intended utility and the viewer.