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Here is a small picture from the same data adjusted to 'normal' camera spectral response. Most stars put out some H alpha radiation (unless they have no Hydrogen) and with a H alpha enhanced camera it obviously shows up in the red channel.
The other consideration is that the Hutech LPR filter knocks out Sodium yellow (as emitted by pesky street lights).
It was actually a stack of six images.
I prefer to use the in camera noise reduction as noise shows up on all exposures no matter what the ISO setting. The noise is inherent in the sensor and is more noticeble at high ISO settings as all the ISO setting does is amplify the collected signal in each site along with any noise present.
The other complication is that we humans can barely see H alpha anyway so if we want to portray it in any nebula it will also show up elsewhere.
Most people are used to widefields produced by colour film which is carefully formulated to have the same spectral sensitivity as the normal human eye.
One exception was Tech Pan B&W film which had good response to H alpha.
If you have any futher questions will do my best to answer them. Maybe I should do a short article on the human visual system and its colour response.
Most people do not realize that the brain does an automatic white balance in real time no matter what the natural lighting conditions and or colour distribution/composition inherent in the scene being viewed.
Bert
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