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2022-05-29: APP 2.0.0-beta2 has been released !

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windows 2.0.0-beta2

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Stacking artifacts


(@donkrx)
Brown Dwarf Customer
Joined: 2 months ago
Posts: 13
Topic starter  

So I'm working on my Milky Way image, which I took a lot of (untracked) subs for (100). I attempted to manually adjust my camera position between shots a couple times. After integrating to a reference frame (and only attempting to fix vignetting) I get obvious dark edges of the frame on the image. I have to do a huge crop to fix this. I set MBB to 15% during this integration but it doesn't help, I think it's just my fault from shooting?

Questions: can this be corrected at all in APP without cropping, or do I need to do something in PS or another program, and how should I go about shooting next time to minimize this problem? Maybe don't move my camera?

2 MilkyWay RGB session 1 vc St

.


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4850
 

If these are true gradients then it should be possible with the light pollution tool. But what were the conditions like, lots of light pollution? It can become challenging in cases for sure. Did you use calibration frames?


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(@donkrx)
Brown Dwarf Customer
Joined: 2 months ago
Posts: 13
Topic starter  

I was in a decent Bortle 3 location but pointed towards some LP I believe. East side of Joshua Tree. No calibration frames, I was told not to bother with them by others for 14mm MW shots.

The dark borders are not true gradients. I enabled LNC and that helped with the dark borders showing. Running with higher order/more iterations now.

If I can't get rid of the borders entirely, should I be cropping it before attempting vignetting correction?

And does LP removal need to be done before or after vignetting correction or does it not matter?

Thank you Vincent for bearing with me. I am a total newbie here.


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4850
 

No worries, I was a total newbie back in 2015, we all start at some point. 🙂

Usually I perform LP correction after the mosaic is created.

I would definitely still use calibration data, darks, flats and flat-darks will be helpful for each frame for sure (as with all data basically). Better corrected data per frame will always help with further processing. If you want we can have a look at the data and give it a go as well?

If so, you can find the instructions to upload on the top-right of the forum. Please notify us if you did that. 🙂


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(@donkrx)
Brown Dwarf Customer
Joined: 2 months ago
Posts: 13
Topic starter  

Thanks for offering to help. I may take you up on that but want to put in more effort myself before I bother you with that.

I just want to clarify: LP removal should be done before vignetting correction, or it doesnt matter which is done first?

I will attempt to take calibration frames since I believe I can meet all the criteria (focus position is saved and temp at night here matches when I shot).


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4850
 

Vignetting correction is usually done with the use of flats. If you don't have those, you can try the artificial flat option (I can explain how), but that isn't ideal. If that's the only option you have, of course you can go for that. And then you should be left with actual gradients from light pollution. In that phase I'd go for the LP correction.


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(@donkrx)
Brown Dwarf Customer
Joined: 2 months ago
Posts: 13
Topic starter  

Hmm. I just did LP removal alone and it seemed to get rid of both LP and vignetting. Anything wrong with that approach?

I spent ALL weekend working on my stack and was pretty successful I think. I watched Mabula's videos 2-3 times each and there are definitely some critical tips in those videos (stated somewhat casually so don't miss them).

For any newbies like myself reading:

1. Enabled LNC in 6) Integrate. Increased iterations and degree until normalization looked good. Algorithm also converged on 2nd degree after 3 iterations so no more were actually required than 3.

2. Enabled MBB set to 25% because my frames have up to 20% thats not overlapping due to a working time of 1 hour and not tracking. Not sure if this was necessary because I enabled LNC at the same time I changed MBB (I know this is a dumb process to change two things at one time, but it takes so long to integrate I just can't do one thing at a time), but I _think_ it makes sense.

3. LP removal took a lot of boxes since I had both LP and vignetting. I eventually got the background flat and neutralized but you have to keep throwing boxes around until it flattens out (one thing I didn't try was increasing box size). With such a wide angle shot at 14mm pointed at the horizon, I think the LP removal is harder (compared to zenith with longer focal length) because the gradients are so strong? Particularly challenging is the bottom right of my image which has both darkening from vignetting AND is the origin of LP on the horizon!


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(@vincent-mod)
Quasar Admin
Joined: 5 years ago
Posts: 4850
 

Nothing wrong with an approach that works for you! I'd still suggest to go for flats as well as that makes life a lot easier (though taking flats can be a challenge as well). But good to read and thanks for sharing!


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