Nebulae are clouds of dust and gas that emmit light (emmision nebulae) or reflect starlight (reflection nebulae)
Emission nebulae
In emission nebuale the gas is heated by the radiation of bright hot stars in the vicinity. As a consequece the heated gas emits light at very specific wavelengths. For three of these wavelengths I have filters to capture that light. these are ionized Hydrogen (Ha) at a wavelength of 656 nm, singely ionized Sulfur (Sii) at 672 nm and double ionized Oxygen (Oiii) at 500 nm.
Left: Fly nebula (NGC 1931); center: Fly nebula (IC 417) in SHO Pallete. Sii: 117 x 6 minutes, Ha : 59 x 6 minutes, Oiii : 57 x 6 minutes ; 22,5 hours total.
These 3 channels can be combined to form an RGB color image. Most of the time the Hubble SHO color pallete is used for that, with Sulfur mapped to red, Hydrogen to green and oxygen to blue.
Heart nebula – SHO narrowband color palleteFish head nebula, part of the larger Heart nebula – SHO narrowband color palleteFish head nebula in HSS pallete (more natural color scheme)The heart nebula (NGC 896) is a large emmision nebula in the constellation of Perseus. In my equipment it is just a bit too large to capture it entirely. The Fish head nebula is the ‘point’ of the heart and has its own designation (IC 1795)Messier 1 – the crab nebula – SHO narrowbandRosette nebula - SHO narrowband NCG 1893 ‘the tadpoles’ – SHO narrowbandCat’s eye nebula, a planetary nebula – HOO narrowband (see sectroscopy page for spectrum) SpectroscopyPacman nebula Forax pallete (sulfer – hydrogen – oxygen)Flaming star nebula – monochrome recording of Hydrogen alpha emmision lineBubble nebula – monochrome recording of Hydrogen alpha emmision lineOwl nebula, a planetary nebula from a dying low mass star (HOO narrowband pallete)Western veil nebula (HOO narrowband), part of a supernova remnantEastern veil nebula (HOO narrowband). part of a supernova remnantEastern veil nebula (HSO narrwoband)Messier 27 – dumbbell nebula in HOO (Nikon D5200), planetary nebula of a dying low mass star.Orion nebula – SHO narrowband pallete (QHY294M)Orion nebula in RGB (Nikon D5200 astromodified)Jelly fish nebula (IC 433) – monochrome recording of only Hydrogen alpha emmision lineBubble nebula in SHO palleteCone nevel – SHO color palletteCrescent nebula (in HOO) and spectrum of WR 136 (click for the spectrum)Crescent nebula in Ha
The Crescent nebula in monochrome Ha recording. The central star in the nebula is a very massive Wolf Rayet star that has shed most of its outer layers. The spectrum (taken by me with a star analyzer diffraction grating) allready show materials deeper inside the star. These massive stars are certain to undergo a core collapse in the future when in the core fusion into Iron starts. The core implodes and a Supernova follows. These stars are very rare. Only 200 are known in the Milky Way. That is because massive stars are rare in itself, and the Wolf Rayet phase is short, in an astronomical sense.
Crescent Nebula in HOO, hydrogen (red) and oxygen (blue)Elephant trunk nebula – monochrome recording of Hydrogen alpha emmision lineWizzard nebula Elephant trunk nebula – monochrome recording of Hydrogen alpha emmision line Tulip nebula (emission nebula), plus the jet from the Cygnus X-1 black hole that creates a shock wave where it collides with the intersellar gas.The horsehead and flame nebula. The bright star is Alnitak, the left star from Orions belt. 20×5 minutes for Ha, Sii and Oiii
Reflection nebulae
in reflection nebulae star light is reflected of dust clouds surrounding the stars. There ar bright and dark nebulae. The dark nebulae are particularly hard to photograph, as the level of light is very low.
The Iris nebula below is an example of this, whith its brownish dust clouds. The Infrared light recordings show a bit more of the stars that are in and behind the dust clouds. In the pictures without infrared light mixed in there are less stars visible in the clouds.
Iris nebula, with infrared light mixed in to the luminance channel. Iris nebula – without infrared exposures – The Pleiades cluster, a group of stars that happens to travel through a dust cloud.
