Orion

This is the raw 4 min exposure with a green colour cast caused by sky glow.

Frame 2.
The background is calculated and subtracted from the original ( Frame 1). Looking better !

Frame 3.
A crop of the central part of frame 2 showing the 3 stars in the belt and M42.
The RGB levels are adjusted to show the nebulous regions
NGC 2024 can be clearly seen adjacent to Zeta Ori. as can nebula I.C 434

Frame 4.
A enlarged view of frame 3 around Zeta Ori. The level of the red channel has adjusted to show a glimpse of the Horse Head Nebula, arrowed.