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Mar 28 2026 APP 2.0.0-beta40 will be released in 7 days.

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[Solved] Strange stars with Nikon D5500

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(@maxthebuilder)
Red Giant
Joined: 8 years ago
Posts: 39
Topic starter  

Hello,

I have two D5500 cameras.

One is astro-modified and I use it quite often for astrophotography with great results. Use APP for stacking.

The other one is not modified and I normally use it for very wide-field (nightscapes, etc). Usually stack with Sequator.

This weekend I shot the Orion region with this un-modified camera and 24mm lens. 288 frames...
Stacked with DSS because it's very fast - great result!
Then I thought that APP could do better - but oddly, APP produced a result inferior to DSS.
The brightest stars look really strange.
I am puzzled as to why...
See below:

DSS

orion dss frag

APP

orion app frag

Any idea?

Thanks!

Max


This topic was modified 2 years ago by maxthebuilder

   
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(@maxthebuilder)
Red Giant
Joined: 8 years ago
Posts: 39
Topic starter  

I experimented some...

If I open a single light frame with different software:

APP, Sequator, Affinity, Photoshop, ACDSee look similar and show saturated star cores and red halos (BAD).
DSS, Siril, Pixinsight look similar and do not show saturated star cores and red halos (GOOD).

Similar situation is with stacking:

APP, Sequator, Affinity are similar and show saturated star cores and red halos (BAD).
DSS, Siril, Pixinsight are similar and do not show saturated star cores and red halos (GOOD).

Just reporting...



   
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(@wvreeven)
Quasar
Joined: 8 years ago
Posts: 2134
 

@maxthebuilder The stars in the DSS image that you posted here look saturated to me as well. The halos are smaller than in the APP image but they are still there.



   
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(@maxthebuilder)
Red Giant
Joined: 8 years ago
Posts: 39
Topic starter  

Wouter,
Yes, you are right but the difference is obvious.
I cannot use the stack produced by APP.
DSS on the other hand is quite acceptable.

Posted by: @wvreeven

@maxthebuilder The stars in the DSS image that you posted here look saturated to me as well. The halos are smaller than in the APP image but they are still there.

 



   
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(@astrogee)
Black Hole
Joined: 8 years ago
Posts: 222
 

@maxthebuilder I agree, its not looking good. It seems like too much processing going on



   
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(@mabula-admin)
Universe Admin
Joined: 9 years ago
Posts: 5056
 

Hi @maxthebuilder @wvreeven @astrogee,

The APP result with these saturated colors is the result of having the camera matrix enabled in 0) RAW/FITS. This is a relatively new setting in APP for regular consumer camera's like Canon, Nikon, Sony etc.... If you enable the camera matrix, APP will produce colors as intended by the camera manufacturer, from sensor colors to linear RGB. If you disable the camera matrix, you will get just the sensor colors which should look identical to DSS.

If you use a modified DSLR, the camera matrix setting should be turned off really because that matrix assumes a non modified camera of course.

On some forums there is a big debate about this camera matrix, some claim it is essential to be able to get good colors with OSC camera's, others claim it is not so important 😉

So simply turn off the camera matrix in 0) Raw/Fits and reprocess and let us know if all is okay now.

We at least provide the option to enable/disable the camera matrix, i do not think that DSS nor Pixinsight nor Siril provide this ?

Mabula



   
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(@astrogee)
Black Hole
Joined: 8 years ago
Posts: 222
 

Thanks @Mabula, This feature is excellent for normal DSLRs. I asked Siril developers about this a while ago now and they didn't seem to know what I was talking about. Our friend at Stark Labs had this matrix in Nebulosity but it was really hard to know what numbers to put in - had to do it manually. I'm glad to see the feature is now in APP. As for how important it is it's certainly debatable as it can seem like marginal effect. However, anecdotally it seems to me that the images taken with a stock DSLR have better colour and better star colour than with an Astrocam, where the colour matrix is ignored.



   
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(@mabula-admin)
Universe Admin
Joined: 9 years ago
Posts: 5056
 

Hi @astrogee,

Yes, it is rather a technical and scientifical discussion, and maybe also a subjective one as well. Personally, I think the camera matrix is very important for normal daylight photography and I would think most people would agree to that. But for astrophotography I think nothing is wrong with simply using the sensor colors as starting point in processing. At least we provide this option now for the user 😉

Mabula



   
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(@maxthebuilder)
Red Giant
Joined: 8 years ago
Posts: 39
Topic starter  

Mabula -

Yes, it all boiled down to the camera matrix and white balance.

I had no idea this feature was introduced...

Stacks from my modified DSLR started to look strange back in June (beta 15 : ).

Turned that off and now everything is good again.

Thanks!



   
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