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| so during my post process, I have photoshop, after usually my first stretches, I do the subtract background to make it pop more. I follow all these different tutorials online, how come everyone they do it and subtract the backround it becomes , darker and more clear , everything i do the same technique and subtract the backround my image turns all blue, it gets a heavy blue tint all around I don't understand what I'm doing wrong, I can try to post a picture if this doesn't make sense but its driving me nuts! Please help!!! |
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So this top one is after the BG was removed and the 2nd one was after the first stretch. as you can see when BG gets removed its turns everything a weird glow. this also happened on my NA nebula photo, so i had to not remove the BG and work around it... all the things i see online and youtube when they remove the backround it comes so much more clear and dark this just looks gross .  |
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| Have you tried doing your calibration in DSS? Then stretch the result in PS. |
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Yes, so this image was put together in DSS, 250 lights at 15 sec exposure, 50 flats 50 bias 50 darks, stacked them all, took the highest score for reference frame and so on, idk why it's doing this, it's makes the images so ugly im stumped |
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I have a question, and I am a novice at this, with this being my first year of doing Astrophotography, but I haven't heard anyone talking about Background removal before. I have heard and done where the stars are removed from a photo, you edit the Nebula or galaxy, and then you can put the stars back into the image at the end. I googled, and didn't see anything about Astro background removal. Can you link one of them. Then if I may ask, why are you trying to remove the background? Sorry if the questions sound silly.  |
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Jim Fox: Usually the background it light pollution or even natural sky glow, that's why we usually want it removed. As a plus if done correctly it will align the three colors (make sure R, G, B start from the same point in the histogram thereby ensuring the parts of the image that should be black do not have a hue). Of course if you are not careful you might end up subtracting too much (or too little) so one must tell the algorithms exactly which parts of the image are supposed to contain black background. See e.g. here for a detailed walkthrough of the procedure in PixInsight . Of course PixInsight is not the only program with such a tool, I am only providing the link as an example of the difference background extraction can make. https://www.lightvortexastronomy.com/tutorial-reducing-light-pollution-effects-removing-gradients-and-artificial-flattening.html Cheers, D. |
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| @NyrKorey, how do you subtract the background in Photoshop? I am asking because I don't have Photoshop, I have always used astrophotography programs for this task (Siril, APP, Pixinsight, IRIS). I know it can be done with curves and feathered masks but I don't think it is so easy to get right. From what you are describing, (and the fact your stretched image has a brownish background, brown = red + blue) you are doing something wrong in the blue channel. |
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| So usually my process is, ill open up a new tab in PS, and copy the image to the new template, i would go to filter. Dust/scratches and remove it until nothing really shown and if i need to touch some spots up, like bright stars that are still shining through a bit i will, then save it, go back to my main image go to "apply image" and click the template I just did before and apply it to subtract. Then thats where it gets gross.. thanks for all the replies ,im also still new to all this. How do you go about knowing your taking the right amount of color away? I'll have to find a tutorial on how to do this maybe off a different site then photoshop. |
