Walking noise on comet image

[AstroNebulee]

I have tried stacking my comet c2022 E3 ZTF images in deep sky stacker following the videos on YouTube. But if I stack for comet and stars combined the stars have colour bit the comet doesn't. 

Then if I stack for just stars and again for just the comet the colour is fine on both but I get a lot of walking noise on both images. 

Here is a siril screen shot of just the comet image on autostretch. 

I have seen a thread for stacking the comet in siril but it seems quite a complicated process I may have to get my head around when I have more time. 

The image is 36x60 sec with 30 dark, flat and dark flats. 

Please don't suggest PI no way I can afoord that or have the brain power for it haha. 

Cheers 

Lee 

[bomberbaz]

Lee, it is a very fast moving comet, 36 minutes is going to have movement no matter what you do.

Try reducing the number of frames and go for say 10 of the best consecutive minutes with just darks, you may not need dark flats and flats.

If there is still walking try 8. It is so bright you won't need much.

Edited February 11, 2023 by bomberbaz

[happy-kat]

I too noticed this but I also also got a comet + stars stack out of DSS that has colour on both, this has made wonder how I managed this

[AstroNebulee]

2 hours ago, bomberbaz said:

Lee, it is a very fast moving comet, 36 minutes is going to have movement no matter what you do.

Try reducing the number of frames and go for say 10 of the best consecutive minutes with just darks, you may not need dark flats and flats.

If there is still walking try 8. It is so bright you won't need much.

Hi Steve 

I'll try stacking less and see how that goes. Thank you 

[AstroNebulee]

1 hour ago, happy-kat said:

I too noticed this but I also also got a comet + stars stack out of DSS that has colour on both, this has made wonder how I managed this

I shall have to investigate more on this. Some people have manged it ok with DSS and some haven't. 

[Elp]

There's a tutorial on sirils website how to do it. I tried DSS first, Siril gave a better result. My stack was 222 frames over an hour. When stacking the comet you have to do stringent kappa sigma rejection, I settled on figures of 1 and 2, the beauty with Siril is that it's quick to adjust figures and see the results. You might still have star trailing but with heavy rejection they become thinner and less apparent, the rest you have to apply a subtraction frame to your image and then paint out any left over, there might still be a few, a motion blur will sort it out and layer it on top of a frame which is untouched for detail and blend them via opacity difference.

Then layer on top of a cleaned star image and finish.

Edited February 11, 2023 by Elp

[AstroNebulee]

13 hours ago, Elp said:

There's a tutorial on sirils website how to do it. I tried DSS first, Siril gave a better result. My stack was 222 frames over an hour. When stacking the comet you have to do stringent kappa sigma rejection, I settled on figures of 1 and 2, the beauty with Siril is that it's quick to adjust figures and see the results. You might still have star trailing but with heavy rejection they become thinner and less apparent, the rest you have to apply a subtraction frame to your image and then paint out any left over, there might still be a few, a motion blur will sort it out and layer it on top of a frame which is untouched for detail and blend them via opacity difference.

Then layer on top of a cleaned star image and finish.

Thank you Elp I will give siril a go today hopefully. It certainly is very different processing a comet image 

[Enceladus Dan]

Hiya Lee, 

Have a go with the Sirill guide "working with comets" already mentioned, for me it worked well. I made two images as it stated but found over the 80 minutes (40x120s) my star aligned image had comet artifacts that were longer than the comet stack. So I ended up using only 1 frame for the stars when I combined them in gimp. 

The star trails are still just visible but better, looking forward to seeing your final image, as I can see a nice long ion tail in your image, which I never managed to capture in mine. 

Danny

[Elp]

If you draw an opacity or layer mask around the comet stack (around the comet with a soft brush), the majority of your star trails in the comet stack will be gone. Then layer that on top of a star only image.

[AstroNebulee]

6 hours ago, Enceladus Dan said:

Hiya Lee, 

Have a go with the Sirill guide "working with comets" already mentioned, for me it worked well. I made two images as it stated but found over the 80 minutes (40x120s) my star aligned image had comet artifacts that were longer than the comet stack. So I ended up using only 1 frame for the stars when I combined them in gimp. 

The star trails are still just visible but better, looking forward to seeing your final image, as I can see a nice long ion tail in your image, which I never managed to capture in mine. 

Danny

Hi Danny 

Nice image 👌

I tried the siril process and didn't get a good as image as I would of liked. The comet had a double nucleus and didn't look any better for more work. So I'm just going to use the stars stack and separate comet stack from dss and use those. 

6 hours ago, Elp said:

If you draw an opacity or layer mask around the comet stack (around the comet with a soft brush), the majority of your star trails in the comet stack will be gone. Then layer that on top of a star only image.

Hi Elp

I will try this on my next process of the comet thank you Elp. So do I open a new layer and mask the comet and tails with a soft brush, then paste this onto the stars only image? 

Early signs from my first effort are encouraging (without doing the layer mask) so far but need to reprocess this further to bring the ion tail out more. 

Lee

Edited February 13, 2023 by AstroNebulee

[Elp]

I'd say your image looks pretty good as it is.

If you do want to proceed with the layer mask (I'm assuming you're using PS?):

1. With the comet only stack, right click your layer (it might be a background later) and "layer from background" option.

2. At the bottom of the layers window there's a button, think it's a white rectangle with a black circle in the middle or the opposite colour scheme (or just choose from the menu), that's your layer mask button. It'll add a layer mask layer to the right of your image layer, click on the layer mask layer (you'll eventually make a mistake at some point thinking you're painting your layer mask wondering why nothing is happening in the main view, usually it's because the layer mask layer isn't selected but the image layer).

3. On the layer mask layer select a brush, make it large with a soft falloff, painting white will mean that area is visible, painting black will make it invisible, by default is all 100% white, any grey in between or if you paint white with less than 100% opacity will be semi transparent until you paint over the same area a few times making it 100% opaque. Simply paint what you want visible or invisible.

That's it really, you can right click the layer and "apply layer mask" if you want, or just leave it there to adjust again later. it's a good way of layering similar layers to blend them into one image, or sometimes I duplicate a finished dso image and change to soft light/luminosity add a bit of blur or sharpen or high pass to bring out some more detail then blend it via layer mask rather than lasso selecting.

Edited February 13, 2023 by Elp

[AstroNebulee]

29 minutes ago, Elp said:

I'd say your image looks pretty good as it is.

If you do want to proceed with the layer mask (I'm assuming you're using PS?):

1. With the comet only stack, right click your layer (it might be a background later) and "layer from background" option.

2. At the bottom of the layers window there's a button, think it's a white rectangle with a black circle in the middle or the opposite colour scheme (or just choose from the menu), that's your layer mask button. It'll add a layer mask layer to the right of your image layer, click on the layer mask layer (you'll eventually make a mistake at some point thinking you're painting your layer mask wondering why nothing is happening in the main view, usually it's because the layer mask layer isn't selected but the image layer).

3. On the layer mask layer select a brush, make it large with a soft falloff, painting white will mean that area is visible, painting black will make it invisible, by default is all 100% white, any grey in between or if you paint white with less than 100% opacity will be semi transparent until you paint over the same area a few times making it 100% opaque. Simply paint what you want visible or invisible.

That's it really, you can right click the layer and "apply layer mask" if you want, or just leave it there to adjust again later. it's a good way of layering similar layers to blend them into one image, or sometimes I duplicate a finished dso image and change to soft light/luminosity add a bit of blur or sharpen or high pass to bring out some more detail then blend it via layer mask rather than lasso selecting.

Thank you again Elp, yes it's PS cs4, you've explained well to a baffoon like me. I shall give it a go. And thank you for kind words. 

 

Lee 

Edited February 13, 2023 by AstroNebulee

[Enceladus Dan]

2 hours ago, AstroNebulee said:

Hi Danny 

Nice image 👌

I tried the siril process and didn't get a good as image as I would of liked. The comet had a double nucleus and didn't look any better for more work. So I'm just going to use the stars stack and separate comet stack from dss and use those. 

Hiya Lee, it was a bit confusing to read, and I agree the result i got wasn't as good as i had hoped, but better than my first DSS attempt. I finally got a good result with PI. But your new image with DSS and Sirill combo looks fantastic. 

 

Danny

[carastro]

I got the same with DSS and when I had the comet only image I had to (as said above) draw a line around the comet and do some noise reduction to the area around it.  I then combined it with the 2nd result of just stars (the next step in the comet stacking procedure.

Carole 

 

Edited February 13, 2023 by carastro

[AstroNebulee]

1 hour ago, Enceladus Dan said:

Hiya Lee, it was a bit confusing to read, and I agree the result i got wasn't as good as i had hoped, but better than my first DSS attempt. I finally got a good result with PI. But your new image with DSS and Sirill combo looks fantastic. 

 

Danny

I think the Siril workflow could do with a bit more instruction in it as I got lost several times and I'm not always a baffoon haha. Thank you for your kind comments. I'm going to stick with the dss way of stacking comet then stars separately. 

1 hour ago, carastro said:

I got the same with DSS and when I had the comet only image I had to (as said above) draw a line around the comet and do some noise reduction to the area around it.  I then combined it with the 2nd result of just stars (the next step in the comet stacking procedure.

Carole 

 

Thank you Carole. This comet processing is a whole new ball game isn't it. I will try masking the instructions from Elp and see if it fares better on my reprocess. I have a few other sessions I csn have a go on too that were from a day or two after my image. 

Lee