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(@skanker)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 46
December 17, 2018 17:34  

Hello!

Last weekend I've made some pictures of comet 46P Wirtanen and M45.

Canon 6D - Samyang 135mm - ISO 1250 - F3.2

The stack in the drive folder consists of 5o pictures ( + 20 darks 30 flats 30 bias)

https://drive.google.com/drive/folders/1lejQi18FL-0NlBh55dOCepqeS4uF0gM4?usp=sharing

In my opinion the noise is to strong in the final stack... I've also tried to stack the lights in Photoshop ( median) and the result was much cleaner compared to the APP version!

Did I do something wrong in APP?

CS Gernot 

 

This topic was modified 1 year ago by skanker

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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1746
December 19, 2018 02:04  

So could you post the 2 end results next to each other as pictures? It's very likely a difference in stretching for background versus signal (and the processes between the two are very different).

So looking at the stack in APP, I can see there is no correction made during calibration. If the flats would have worked, the dust spots would be gone as well as the light gradient. As such, the actual processing didn't went according to plan.


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(@skanker)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 46
December 19, 2018 09:47  

I used the DSLR-tuorial by Mabula... Maybe i ve made a mistake during the workflow!? 

CS Gernot

This post was modified 1 year ago by skanker

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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1746
December 19, 2018 23:16  

Maybe or the calibration data you have isn't good enough, it's possible. The image below shows gradients and dust still present, which should've been corrected by the calibration frames (and remaining gradients from light pollution can be corrected in the Tools menu). You can always send me a few flats, darks, bias and lights to see if I can tell if something is wrong there.

Screenshot 2018 12 20 at 11.10.55

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(@skanker)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 46
December 20, 2018 18:27  

At first thank you for your support Vincent 🙂

I've uploaded the masters and a flat to the drive folder. Maybe you can check out the files and judge them!

Additional info:

-The gradient in the stack is moonlight. 

-The reason why the flats can't correct the dustpoints is maybe that I've created them the morning after the shooting session ( the lens was moved).  I hope this is english and you understand what I mean haha 🙂

 

CS Gernot

 

This post was modified 1 year ago by skanker

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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1746
December 20, 2018 21:13  

Yes I get it. 😉 I'm not sure what you mean with the drive-folder though, do you have a link to it you can share with me? You can send it to vincent@astropixelprocessor.com


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(@skanker)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 46
December 20, 2018 21:22  

I meant the Google Drive - link in the first posting 🙂 Klick on the link and you will find the added data!

https://drive.google.com/drive/folders/1lejQi18FL-0NlBh55dOCepqeS4uF0gM4?usp=sharing

Cheers Gernot 

This post was modified 1 year ago by skanker

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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1746
December 21, 2018 00:06  

Ahhh, sorry. 🙂 Will check it out thanks.


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1746
December 22, 2018 21:42  

So I don't see a lot of things wrong, but the flats might be. A good way to get those right is to have a very even illumination (e.g. with a flat-panel) en going for exposures close to a second. Sequence Generator Pro has a nice calibration wizard for that (using the DLSR built-in histogram to check isn't the best way, but if you do, aim for a peak at around 80% of that range). I also wonder if you changed the focus when taking the flats? It's vital not to change that as it also might be the dust is now out of focus.

Further, take more data, also for the darks and bias. For darks I go for at least 60 or so, but I made a few at 150 (that's a lot yes, but statistically a nice target, I just let the dslr shoot in a dark box outside when it's cloudy). Bias is easy as it's fast, so 100 is a nice target. If that's too much for you, you can get away with around 50 for both. For the lights, also more data will help reducing noise. Noise will always be there ofcourse, I just take it for what it is as I'm more interested to bring forward very weak details instead of wanting an almost black background (which does require good calibration as your dust spots will pop up a lot then). The moon light pollution can be corrected using the Light Pollution tool in the tools tab (9).


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(@skanker)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 46
December 23, 2018 11:41  

Thanks for checking the files! Next time I will make more calibration pictures. I'm also worried about the flats... I produce them with the "white t-shirt"-method because a flat-box is so expensive. Maybe that's not accurate enough!?

screenshot

This is a 250% view of the stack... I thought after stacking nearly 50 pics the noise would be reduced more. I think the color mottle is extreme !?

Is that normal ?

CS Gernot 

This post was modified 1 year ago 2 times by skanker

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(@whixson)
Neutron Star Customer
Joined: 2 years ago
Posts: 115
December 24, 2018 07:51  

You might want to try dithering between frames to reduce the mottling. Tony Hallas has a good video on YouTube about DSLR astroimaging that goes over this and other techniques. 


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(@astrogee)
Red Giant Customer
Joined: 2 years ago
Posts: 84
December 24, 2018 17:08  
Posted by: Vincent Groenewold - Moderator

So could you post the 2 end results next to each other as pictures? It's very likely a difference in stretching for background versus signal (and the processes between the two are very different).

So looking at the stack in APP, I can see there is no correction made during calibration. If the flats would have worked, the dust spots would be gone as well as the light gradient. As such, the actual processing didn't went according to plan.

Hi Vincent, How do you know there is no correction made? Are you looking at the filename? The fits header? I would like to be able to confirm this without a doubt because I need to take flats untethered to get the correct exposure with high ISO. I need to verify that the flats (which have different size from the lights) are in fact used in the flow. Thanks.

PS: Here is an example filename from my last stack: St-med-3605.0s-NR-x_1.0_LZ3-NS-full-eq-add-sc_BWMV_nor-AAD-RL-noMBB


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(@skanker)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 46
December 25, 2018 13:15  

At first merry christmas to all of you 🙂

@ Whixson

I think dithering isn't possible with my equipment...

As Vicent said, the key is the use of more darks and more bias!

Does somebody know if color mottle will increase with higher iso settings?

CS Gernot 

 


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1746
January 2, 2019 22:29  

I just looked at the end result and still saw dust in the frame, which indicates the flats were either wrong or not used during processing. It looks like there was a problem with the flats themselves.


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(@skanker)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 46
January 7, 2019 12:39  

Thx for your help Vincent! I think the flats were the problem...

In my later project of NGC 7000 everything worked fine 🙂

https://www.astropixelprocessor.com/community/gallery/ngc-7000-lrgb/#post-4860

CS Gernot


(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1746
January 9, 2019 02:40  

Ahh awesome!


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(@mabula-admin)
Quasar Admin
Joined: 3 years ago
Posts: 2416
January 9, 2019 22:48  

Dear Gernot @skanker @vincent-mod,

I have read the enitre thread, do you think this still needs a clarification regarding the amount of noise after stacking 50 frames?

If so,then you will need to provide all light frames and the masters on the Google Drive, so I can make the integration myself and give you feedback. Right now, I only see the Masters on Google Drive, right?

I will be able to tell if you masters are okay or not, and whether noise reduction from stacking is working well or less well for some reason 😉

Cheers,

Mabula


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(@skanker)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 46
January 10, 2019 07:45  

Hello Mabula!

There is no need for this... thank you 🙂

Cheers

Gernot


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(@mabula-admin)
Quasar Admin
Joined: 3 years ago
Posts: 2416
January 17, 2019 18:37  

Excellent, thanks Gernot @skanker 😉


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(@tsa120man)
Brown Dwarf Customer
Joined: 2 months ago
Posts: 6
April 5, 2020 23:36  

Hi - Maybe you can help me out.  First, let me say that I'm a total novice with using your software and recently downloaded the trial version of APP  to see if I wanted to purchase it.  I did a test run with the Leo Triplet using all three platforms - APP, PI and PS.  The only one that came out excessively noisy was APP.   I loaded 22 lights of the  Triplet and 30 each of bias, dark and flat frames and then used the APP automatic integration process using all defaults.  I didn't touch any of the intermediate steps - calibrate, analyze stars, normalize, etc.   The resulting stack looks pretty good except for what I think is excessive noise.   I suppose I could export to PS and reduce the noise there but would like to understand what APP can do for noise reduction.  Any guidance you could provide would be most helpful.  Attached is the file for your information.  The jpg compression doesn't really show the noise as much as the original APP file but that was too big too attach.  Thanks!

Leo Triplet April 5 2020 St

 

Paul O'Brien; State of Washington, USA


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