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Advice about noise reduction and clarity?


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Hello there,

I am completely new with posting to this forum but after getting interested, reading this forum and shooting my first astrophotograph I have a question about processing.

This image was shot yesterday: http://www.astrobin.com/120604/

Gear and setup: a Nikon D3200 on a very sturdy tripod (no tracking) with the 18-55mm kit lens on 18mm at f/3.5 with ISO 400. I made 20 images, 20 seconds each so a total of 6m40s. I stacked them with DeepSkyStacker with default settings since I'm totally not familiar with the program yet and processed in Photoshop (I did the best I could get out of the image).

Please let me know what I can improve during imaging, setup, processing, stacking etc. I love to get better quality, clarity and less noise. If someone would like to have a look at my stacked tiff, I can upload that as well so please let me know.

Thank you!

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welcome to SGL

looks like you have some problem with the stars on the left hand side

maybe inspect your subs for bad shots and remove them and restack

Thanks! I checked them but I cannot find an image which has those artifacts but since these were captured over 15 minutes or so, the stars have moved ofcourse. Did DSS just stack them next to each other which causes the 'trails' or might there be some other problem?

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the stars on the right look Ok so it looks like another issue possibly something in the optic train
Dss scores the frames I tend to do that then reject any with a low score

but the problem gets worse the further left you go, to me that suggests somethings not flush or tilted (like a collimation error)

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I'd try just stacking the first and last image - see if the same effect occurs. Then add in one image at a time until the the result shows this. It doesn't seem to be trailing, or a gradual change - it looks like one of images that's "different" from the others.

It could be some sort of shift in image scale with DSS only registering stars on the RHS as alignment stars. Though don't ask me how that could happen. :huh:

Or if there is no obvious reason,  just crop off the LHS side of your images. There's no law that says all images have to show the full captured frame.

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the stars on the right look Ok so it looks like another issue possibly something in the optic train

Dss scores the frames I tend to do that then reject any with a low score

but the problem gets worse the further left you go, to me that suggests somethings not flush or tilted (like a collimation error)

I just pointed the camera almost vertically to the sky, maybe my tripod wasn't locked well but that would show up on the individual frames (which it doesn't). Well, it's my first try so I'll give more attention to aligning the tripod the next time!

I'd try just stacking the first and last image - see if the same effect occurs. Then add in one image at a time until the the result shows this. It doesn't seem to be trailing, or a gradual change - it looks like one of images that's "different" from the others.

It could be some sort of shift in image scale with DSS only registering stars on the RHS as alignment stars. Though don't ask me how that could happen. :huh:

Or if there is no obvious reason,  just crop off the LHS side of your images. There's no law that says all images have to show the full captured frame.

With all my images in DSS the starmask does only point to stars in the most right 60% or so of the frame. The LHS does not have stars in it, that should have given me a hint but it's the first time using DSS for me. I'll try the technique you outlined when I have some time left, and I'll let you know if it solves anything, thank you!

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Hello again,

I was able to process the image further with better results in my opinion. I cropped the image like you suggested and tried to process that better in Photoshop. 

Here is the result: http://www.astrobin.com/120689/

Do you have any tips to bring out a better view of the stars; or is it just that I need to make more photos to stack with a longer shutter time? 

Thanks everyone for the suggestions already. 

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If you have sigificant lens distortion and field rotation (as caused by e.g. imaging from a fixed tripod or alt-az mount), then I don't believe DSS will be able to align the images correctly. You would need to correct for the lens distortion before loading the images into DSS.

NigelM

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If you have sigificant lens distortion and field rotation (as caused by e.g. imaging from a fixed tripod or alt-az mount), then I don't believe DSS will be able to align the images correctly. You would need to correct for the lens distortion before loading the images into DSS.

NigelM

I will look into that the next time, didn't think about that, thanks!

You have some lovely star colours captured there. I would suggest stopping down to f4 or f4.5 and having a look at your focus if you try another image. It looks just a little soft to me.

Phil

I noticed that as well, but since there is a lot of light pollution here I wanted to use the largest opening as possible. Will try stopping down a bit when I found a darker location :)

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