Trying to wipe M31

Questions and answers about processing in StarTools and how to accomplish certain tasks.
mgutierrez
Posts: 59
Joined: Sat Oct 24, 2020 11:07 pm

Trying to wipe M31

Post by mgutierrez »

Hi all!

This is my first post in this forum! Thanks for this fantastic software and supporting this forum!
I'm a newbie in Startools and astrophotography in general. I've downloaded the last alpha version (I usually use alpha rather than stable) and I'm quite confused how wipe module works.
My fits file (stacked with dss) is https://www.dropbox.com/s/9bgp3p2f9zo68 ... S.fts?dl=0
Once autodeveloped and automatically wiped, I get:
Selection_004.jpg
Selection_004.jpg (186.64 KiB) Viewed 3560 times
I want to finetune wiping. In particular, this zone delimited by the mask, on the bottom left corner:
Selection_005.jpg
Selection_005.jpg (178.68 KiB) Viewed 3560 times
But after wiping with the mask active, I get:
Selection_006.jpg
Selection_006.jpg (214.98 KiB) Viewed 3560 times
I thought that the only zone affected would be that delimited by the mask. What am I missing? How could wipe only that zone? How could you improve in general the wipe of this image?

Thanks in advance!
happy-kat
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Re: Trying to wipe M31

Post by happy-kat »

try masking the galaxy plus any dust bunnies etc. then wipe
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admin
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Re: Trying to wipe M31

Post by admin »

Using a mask in Wipe does not mean it will get selectively processed (selective processing is something that is best avoided in general in AP).
Using a mask in Wipe tells Wipe where it may sample the image and where it may not;

StarTools' Wipe algorithm works exactly the other way around from other software (PI/Siril/APP).

In StarTools - if at all needed! - you can help Wipe by showing where you are absolutely sure there is no background. To do so you create a mask that includes everything (e.g. made "green"), except for the areas that you are certain there is no background for Wipe to sample.

This is an important improvement over other algorithms where you have to guess where background is (which is almost always hard to see); almost always these algorithms are removing faint nebulosity or are not removing enough gradient, simply because you placed a sample box where it shouldn't have been, or haven't placed a box where it should have been.

E.g. something like this would be appropriate;
StarTools_227.png
StarTools_227.png (452.86 KiB) Viewed 3548 times
When reviewing the result in Wipe, keep in mind that the diagnostics stretch was designed to show your dataset in the worst possible light on purpose. This way you can be sure you have caught all gradients to the best of your abilities. However, when it comes to actually stretching your image for real (e.g. aesthetic purposes), chances are you will want to settle for something much more conservative. E.g. something like this with a good RoI;
StarTools_228.png
StarTools_228.png (319.68 KiB) Viewed 3548 times
With such a stretch, focused on (meant for) bringing out the actual detail, you will usually see that any remaining imperfections become hardly noticeable.

Hope this helps!
Ivo Jager
StarTools creator and astronomy enthusiast
mgutierrez
Posts: 59
Joined: Sat Oct 24, 2020 11:07 pm

Re: Trying to wipe M31

Post by mgutierrez »

Hi!,

Thanks to both of you!!! Absolutely it helps, Ivo, as usual! :thumbsup:
I will give a try and upload my result. Thanks again!

m
mgutierrez
Posts: 59
Joined: Sat Oct 24, 2020 11:07 pm

Re: Trying to wipe M31

Post by mgutierrez »

Hi Ivo,

Please allow me a (surely dumb!) question. How did you manage to define the mask surrounding the galaxy? I suppose that due to the irregular border, it was not done using the lasso tool. But the other ones (by color and/or brightness) skip many pixels and/or require of a huge number of clicks. Or maybe you first masked the galaxy and then inverted. In any case, the question would be the same. I know this is quite basic but I cannot figure out how did you do it.

Thanks again!
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Re: Trying to wipe M31

Post by admin »

mgutierrez wrote: Tue Oct 27, 2020 1:57 pm Hi Ivo,

Please allow me a (surely dumb!) question. How did you manage to define the mask surrounding the galaxy? I suppose that due to the irregular border, it was not done using the lasso tool. But the other ones (by color and/or brightness) skip many pixels and/or require of a huge number of clicks. Or maybe you first masked the galaxy and then inverted. In any case, the question would be the same. I know this is quite basic but I cannot figure out how did you do it.

Thanks again!
No such thing as a dumb question! I used the default Flood Fill Lighter Pixels tool, then clicked the Grow button a few times, then Inverted the mask.
Hope that helps!
Ivo Jager
StarTools creator and astronomy enthusiast
mgutierrez
Posts: 59
Joined: Sat Oct 24, 2020 11:07 pm

Re: Trying to wipe M31

Post by mgutierrez »

admin wrote: Tue Oct 27, 2020 2:23 pm No such thing as a dumb question! I used the default Flood Fill Lighter Pixels tool, then clicked the Grow button a few times, then Inverted the mask.
Hope that helps!
Sorry Ivo I think I'm missing something. I've selected flood fill lighter pixels brush mode, and starting to mask by the core of the galaxy. After 3 or 4 clicks, subsequents clicks only fills a few pixels, or even only one. Since (afaik) I cannot set a threshold, It would take many many clicks to get a reasonable sized mask to be able to grow, since growing the mask only enlarge the size a few pixels. What am I missing?

Thanks again!
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Re: Trying to wipe M31

Post by admin »

mgutierrez wrote: Tue Oct 27, 2020 2:59 pm Sorry Ivo I think I'm missing something. I've selected flood fill lighter pixels brush mode, and starting to mask by the core of the galaxy. After 3 or 4 clicks, subsequents clicks only fills a few pixels, or even only one. Since (afaik) I cannot set a threshold, It would take many many clicks to get a reasonable sized mask to be able to grow, since growing the mask only enlarge the size a few pixels. What am I missing?
The way the tool works is in the name; if you click a pixel, it will look for any neighbouring brighter pixel and fill that as well, then that pixel will look for any neighbouring brighter pixel as well, and so on and so forth.
So what you will want to do, is click on a pixel that is the minimum brightness you wish to fill. In the case of your image, you will want to click on the outskirts of the disc, outside the core.
Ivo Jager
StarTools creator and astronomy enthusiast
mgutierrez
Posts: 59
Joined: Sat Oct 24, 2020 11:07 pm

Re: Trying to wipe M31

Post by mgutierrez »

Thanks again Ivo; I will try again!
mgutierrez
Posts: 59
Joined: Sat Oct 24, 2020 11:07 pm

Re: Trying to wipe M31

Post by mgutierrez »

and this is what I have been able to get...
WhatsApp Image 2020-10-29 at 15.34.56.jpeg
WhatsApp Image 2020-10-29 at 15.34.56.jpeg (350.18 KiB) Viewed 3450 times
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