Stack is noisy

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.

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

CS Gernot

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.

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

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

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 

Ahhh, sorry. 🙂 Will check it out thanks.

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).

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!?

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 

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. 

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

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 

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.

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

Ahh awesome!

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

Hello Mabula!

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

Cheers

Gernot

Excellent, thanks Gernot @skanker 😉

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!

Paul O'Brien; State of Washington, USA

Hi Paul,

So did you do any other steps in PI for it to produce a less noisy stack? I shouldn't be very different, but you're right that APP itself doesn't have a noise reduction algorithm yet. It's high on the development list though.

@vincent-mod

Hi Vincent -  'thanks for your reply.  No, I didn't do anything in PI except to use batch processing to integrate/stack.  I used all default settings too just like I did in APP.  I'd send you the PI integrated image but their xisf file format won't work with jpeg and other file formats and the xisf file is too big to attach here.

I really like the simplicity of APP but the post processing is very confusing and not easy to follow without better documentation/guidance.  The quick guide has a lot of blank pages in it which I assume means that it hasn't been developed yet.  I have no idea how to use the right side of the user interface screen without more guidance either.  I probably need to look at some youtube videos from Sara and others to learn more about APP.  

I don't mean to be critical of APP because I think it shows tremendous potential.  It's just that I find it very challenging to work with at this point.  Maybe I'm not doing something right.  At any rate, keep up the great work and I look forward to future APP updates.  We need people like Mabula, you and others to keep pushing the envelope in the development of new AP software!

Take care and be safe above all else!

Paul 

Hello Paul,

In the integration mode 6)integrate set integrate to MEDIAN and set the WEIGHTS mode to Quality that give you more signal ratio and noise reduction

That give you best results

Keep us inform 😀 

Patrick

@patrick

Great Patrick!  I'll do that.  Thanks!

Paul 

Posted by: @tsa120man

 

I don't mean to be critical of APP because I think it shows tremendous potential.  It's just that I find it very challenging to work with at this point.  Maybe I'm not doing something right.  At any rate, keep up the great work and I look forward to future APP updates.  We need people like Mabula, you and others to keep pushing the envelope in the development of new AP software!

Take care and be safe above all else!

Please be as criticial as you want! It's only good to see where we might have to improve things, so thank you!

The workflow should become easier each time, the automatic settings are one of those examples where you don't really have to change settings to get the best result. Maybe in some situations you might want to change them, that's always possible like Patrick above mentions. I would be surprised though if that is so different in this case.

@vincent-mod

A belated thanks, Vincent, for your follow-up message.  This is pretty funny and somewhat embarrassing but I just discovered a treasure chest of information about APP processing that I didn't realize exist.  I tapped the red question mark on the right side of the user interface and saw that's where all the tips and explanations are located regarding the sliders, etc.! 🙃 .  That should definitely help me learn more about APP!

Paul 

No worries, excellent!

@tsa120man damn I have been looking everywhere for the tool tips

@magicker. 

So, did you find the tool tips under the question mark ok?

YES! finally