Messier 42 (M42), one of the most famous winter target for every astrophotographer, so called Orion Nebula, is an emission-reflection nebula located in the constellation Orion. With an apparent magnitude of 4.0, the Orion Nebula is one of the brightest nebulae in the sky and is visible to the naked eye. It lies at a distance of 1,344 light years from Earth and is the nearest stellar nursery to Earth. The nebula has the designation NGC 1976 in the New General Catalogue.
The image consists of the following data taken by me only:
1.Panel 5 (Core of M42): Ha 76x 300s= 6.3 h
2.Panel 8 (Edge of M42): Ha 105x 300s= 8.8h
Overall: 181 frames, 15.1 h.
Dates: P5 Jan 1st, 19th / P8 Jan 20, 22 , 23 (taken under 80+% moon phase)
Interestingly, when I first processed these 2 panels in APP with linear data, APP gave me bad results and background were totally unmatched.
Thing did not play better with higher degree and iterations set up, and backgrounds of these two panels seemed can never match. See pic below.
Then I guessed it may be the contrast that cause it because P8 was taken under 80% or higher moon phase while P5 was taken somewhere between 40%~60% and suffered from moon light less. After stretched these two panels into non-linear and HDR to P5 as well as ArcsinStretch to P8 in order to achieve better balance between highlights and shadows, I tried again with almost the same setting: 1 degree of LNC and 3 iterations.
Well, This time APP did a good job in mosaic, and gave me a decent result with little unnatural transition around edges.
It seems that for panels with heavy difference on SNR or background darkness, try integrate processed non-linear data may be a better choice once APP cannot blend them together under linear one. 
Location of Remote Observatory: Daocheng Obs, Sichuan,China
Raw data capture and batch pre-process: John Chuhong Yu
Post process: John Chuhong Yu
Hope that you enjoy this image!
Comments