Here are some lushes narrow band images of some famous nebulas built from many hours of data recorded from suburban Sydney, NSW. Many of the sub-frames had strong light pollution gradients associated with light scattered through thin cloud and smog. Light pollution gradients are especially strong during summer when cloud free nights are rare in Sydney. My strategy was to record as many sub-frames as possible across multiple nights to help average away the gradients, and then apply one instance of the PixInsight automatic gradient removal tool to the final integrated image.
https://www.flickr.com/photos/mlparkinson/15976184333/