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Weird patterns on my stacked photo

astrophotography beginner catadioptric Celestron dslr eq SCT
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#1 avodcap7

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Posted 17 January 2021 - 08:06 AM

Hello, 

I imaged M42 last night and got some decent exposures, even with my C8 and Nikon D7200. I didn't guide as I did 60s exposures, plus, the ASIair doesn't work with my guide camera.

I got these weird patterns that ruin the picture.

I was wondering what could cause these patterns on my photo: https://ibb.co/sPTY5W6

Was is because I didn't dither, or is it something else?

 

 

Would love to know!

 

Emilis



#2 Scott Mitchell

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Posted 17 January 2021 - 08:16 AM

Is that a single image, or do these artifacts get generated during stacking?



#3 Tapio

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Posted 17 January 2021 - 09:20 AM

Weird looking.

Do you have any filters in the imaging train ?

I'm offering frost, again, as an explanation, but not sure if it is that.



#4 Midnight Dan

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Posted 17 January 2021 - 09:44 AM

My first thought was frost on the sensor too.  But I have to say, it doesn't quite look like frost patterns I've seen in the past.  Maybe some odd flat interaction.  Did you take flats?

 

-Dan



#5 avodcap7

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Posted 17 January 2021 - 09:50 AM

Is that a single image, or do these artifacts get generated during stacking?

stacked image

 

My first thought was frost on the sensor too.  But I have to say, it doesn't quite look like frost patterns I've seen in the past.  Maybe some odd flat interaction.  Did you take flats?

 

-Dan

I did take flats, maybe it's because I stacked it in DSS

 

Weird looking.

Do you have any filters in the imaging train ?

I'm offering frost, again, as an explanation, but not sure if it is that.

No filters



#6 Tapio

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Posted 17 January 2021 - 09:54 AM

You could browse your raw frames (in DSS?) to see if the pattern shows in them.



#7 Der_Pit

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Posted 17 January 2021 - 09:59 AM

If I load the full resolution one I can see a checkerboard pattern.

Did you drizzle without having dithered?



#8 Midnight Dan

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Posted 17 January 2021 - 10:01 AM

If you took that with a Nikon D700, why isn't it in color?  My guess is that if you process that as a color image, you'll see a rainbow effect going through those streaked edges.  I've seen that when the flats are not properly matched to the lights.

 

-Dan



#9 avodcap7

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Posted 18 January 2021 - 02:04 AM

If you took that with a Nikon D700, why isn't it in color?  My guess is that if you process that as a color image, you'll see a rainbow effect going through those streaked edges.  I've seen that when the flats are not properly matched to the lights.

 

-Dan

I don't really know why they're black/white, but I think it is because I captured them with  ASIair pro which produces .fit files. I still need help on how to debayer them as I don't understand it.

 

As for the flats, yes, they do indeed cause the disturbances. Turns out, I have MAJOR vignetting, and when the flats and/or other calibration images are applied they cause these patterns.

I'll soon get my ASI294MC pro and I think that will fix the vignetting.

But I still would appreciate advice on how to debayer images and get color. Do I need to debayer them before I upload them to DSS, or do I do it later, and how do I do it?

 

Thanks,

Emilis



#10 sharkmelley

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Posted 18 January 2021 - 02:16 AM

But I still would appreciate advice on how to debayer images and get color. Do I need to debayer them before I upload them to DSS, or do I do it later, and how do I do it?

 

Within DSS there is a dialog to set your Bayer pattern e.g. RGGB etc.

 

The artefact you are seeing is caused by aligning and stacking undebayered data.

 

Mark


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#11 avodcap7

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Posted 18 January 2021 - 03:05 AM

Within DSS there is a dialog to set your Bayer pattern e.g. RGGB etc.

 

The artefact you are seeing is caused by aligning and stacking undebayered data.

 

Mark

It's finally working!

Never had this problem before.

 

Thank you very much!

Emilis



#12 mmflytie

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Posted 18 January 2021 - 03:07 PM

So what did you end up doing?



#13 avodcap7

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Posted 22 January 2021 - 11:05 AM

So what did you end up doing?

It was completely because I didn't debayer.




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