I am taking widefield mages using my modified Nikon D5300 with a 400 mm telephoto lens. I keep the exposures short (30 seconds each) but stack many (350 - 400) to get detail. I see horrible background noise in the form of streaking when I do this. Individual images fail to show this issue. I've attached a 3 hour image of the Horsehead to illustrate this. Any ideas on the source of th is and how to process it out? GradientXTerminator fails to remove it.