SouthEastViewer Posted June 19, 2022 Share Posted June 19, 2022 Hi Am new to astrophotography and have begun using a Nikon D5600 and WilliamOptics Z73 based rig. I seem to be constantly getting circular gradients that interfere with any tone stretching leaving circular bands of colour. Example attached below from few nights ago. Does anyone know what could be causing this and how to eradicate it please? All help greatly appreciated. Thanks! Some data on below: - 2 hours of light, at 5 mins per shot - 20 darks, 20 bias, and 20 flats - telescope is in a place where neighbours flood light has some cast, but is pointing away - bortle class 5 area Quote Link to comment Share on other sites More sharing options...
TerryMcK Posted June 19, 2022 Share Posted June 19, 2022 Hi and welcome to the forum. Are you using any light pollution filtering? Quote Link to comment Share on other sites More sharing options...
SouthEastViewer Posted June 19, 2022 Author Share Posted June 19, 2022 Hi Thank you! Yes, I've the following installed: Svbony CLS filter I threaded it into the William Optics Field Flattener. Thanks! Quote Link to comment Share on other sites More sharing options...
GazAstro Posted June 22, 2022 Share Posted June 22, 2022 It's difficult to say but it does look like possibly 2 sources of Lp, maybe Moon on one side and street lights etc from the other. Can you post an unstretched image ? Quote Link to comment Share on other sites More sharing options...
SouthEastViewer Posted June 23, 2022 Author Share Posted June 23, 2022 Hi It seems what I was doing wrong was not properly taking flats. The histogram of my flats was either over or under exposed. When I reduced exposure on the D5600 down to 2 seconds I got a peak in the histogram around 3rd to middle. I redid the biases and on the night took darks too. The results were significantly better. Also, I moved the scope away from neighbour flood light haze. Not sure if that helped much, but every little helps. Here's two consecutive nights worth of Fireworks Galaxy to see if I got rid of excess gradient and noise. Quote Link to comment Share on other sites More sharing options...
TerryMcK Posted June 23, 2022 Share Posted June 23, 2022 Looking much better. Quote Link to comment Share on other sites More sharing options...
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