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Deep Sky Stacker can't align/ find stars

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Hello together,

I tried capturing the milky way a few says ago. This isn't my first time doing astrophotography but I ran into a problem.

I captured 128 light frames, 51 darks and +100 flat and bias frames. I loaded them into DSS and registered them. Firstly I set the threshold so that ~200 stars were found. All pictures have a very similar score (1070-1400) and number of stars (180-220). There were no clouds.

After the first stack the result looked horrible. I looked at the offset data and some images got rotated by over 150 degrees which can't be since all pictures were taken within an hour. Some pictures did't have any offset information at all (NC)! I changed the star detection threshold and tried everything from 15 to 500 stars with the same result. I looked a bit closer which stars got detected and this seems kind of random. The stars that got recognized are not even similar in 2 pictures taken after each other.

What else can I try? I used the Sony A7iii with the Samyang (Rokinon) 14mm f/2.8. It was my first night with the 14mm. I stacked a set of images of the Pleiades a few weeks ago with no problems at all (Sony a7iii, Tamron 70-180mm f/2.8).

Converting the raw images into DNG didn't fix the issue.


Screenshot 2023-03-28 204341.png

Screenshot 2023-03-28 204439.png

Screenshot 2023-03-28 204509.png


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200 stars is a lot more than necessary. DSS uses up to 100, but never more.

However the main problem apears to be that your stars are not round:


as  a result DSS may be rejecting them in favour of noise pixels.

You might be able to get round this by manually selecting stars although with a 100+ images this could be tedious.  

If you can work out why your stars aren't round and fix this, you may well be able to stack next time you try but this data set may be beyond help

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as there is foreground too in your image it would be worth a go to try stacking what you took using sequator, you can mark where the foreground/static objects are in that software

with DSS if there is a better frame with more round stars (probably have the highest score after registering) try marking that as the reference frame

if using 14mm lens then 15 seconds I would have thought might have been ok for little star trailing

Edited by happy-kat
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Posted (edited)

Thanks for the replies!

I know that there is slight star trailing but I thought it wouldn't matter too much (at least it doesn't to me). Maybe the heavy amount of distortion in the corners causes the problem. I will try cropping in all the images a bit so the really bad stars are gone. I will try using sequator as well even as I have stacked an image with foreground before in DSS but who knows...

I also stopped the lens down to f4 to compensate for the vignetting and corner sharpness.


Besides the stacking problem, could you give me some tipps how to improve my astro images? I tried using only one file (the tiff above) but I find it very hard to get a good looking photo out of it. Is it lack in post production skills or are there any limiting factors in the image like heavy light pollution (but I dont think so)?  I use Adobe Lightroom and Photoshop.

Edited by Favo
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I have never heard of the "sony star eater" problem. Just searched it and seems like its a problem with the long exposure noise reduction. If thats right than this cant be the problem since it was turned off and I was shooting in raw.

I didnt change anything in PS, I just converted the ARW file to TIFF in LR but same result with the origninal raw image.


Thanks for helping!

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If you've got a Sony camera for AP the star eater problem is a well known issue. The noise reduction algorithm mistakes small FWHM or dim stars as noise and literally deletes them or makes them less obvious. Even with the setting off this is still applied. The situation is somewhat mitigated if you're doing long exposure enough to saturate the stars so they're not mistaken for noise.

Regarding your issue, if you're having alignment issues usually the best thing to do is manually select your alignment stars, but as others have pointed out, if they're oval, most software will fail to register them. I had this issue during one session when imaging at 1000mm focal length and the guiding wasn't good, I managed to brute force the stacking and it threw away more than half of the subs but in the end I didn't use the data.

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