Using "Multiscale high pass" on deep sky images

Image processing, astrometry, photometry, etc.
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Using "Multiscale high pass" on deep sky images

Post by Rudi » 29 Mar 2020, 14:04

I have been thinking about, how I could get more dynamics in deep sky images with Astroart.

Then I thought about the "wavelets" function, as we know from Registax. Wavelets is using fourier transformations to enhance the dynamics in an image.
This should also be possible to use on deep sky images?

And yes, Astroart 7 do indeed have such function, "Multiscale high pass", MHP, in the Filter menu.
As with Wavelets in Registac, the function should be used gently, or else it will do more damage than good.
You will need to experiment with your own images.

Here's a few examples of what "MHP" can do in Astroart 7

M106 before and after MHP

NGC4217 before and after MHP

An example, step by step

Here, I will briefly show, what I did on my latest image: M106 og NGC4217

You need to carefully apply the MHP on the galaxies areas one by one. You can not apply MHP on the entiere image, that will ruin the stars.

First you need to create a mask, that covers the ares 100%, that you want enhanced, here I am masking the disc in NGC4217:

Once the area is marked, the area needs to be softened, then the MHP impact will gradually decrase towards the borders, use "Smooth" for this:

And now the fun part begins, open MHP from the Tools menu:

If you press the "Preview" padlock icon, then you can watch the effect of the adjustments live.
And by pressing and holding "Compare" button, you can blink the before and after effect.
Be careful, do not over do it ;-)

This is entierely new to me. I dont know, why I haven't thought about this before?
I hope that other AA7 users can use this!

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Re: Using "Multiscale high pass" on deep sky images

Post by agd.alberto » 02 Apr 2020, 17:17

Rudi, thanks, I experimented. Very well

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Re: Using "Multiscale high pass" on deep sky images

Post by it344x » 13 May 2021, 10:54

bumping this thread as it is very, very useful.
If there is a way to create a mask and use the histogram stretch ONLY on the mask section that would enhance this ability even more.
For example, I want to select a galaxy, invert the mask selection and change the rest of the image leaving the galaxy alone, but histogram stretch changes the entire image.

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Re: Using "Multiscale high pass" on deep sky images

Post by dredger » 13 May 2021, 12:47

Thanks for the tutorial on this, very helpful.

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Joined: 17 Feb 2019, 20:54

Re: Using "Multiscale high pass" on deep sky images

Post by WD5IKX » 17 May 2021, 18:07

Great info....I just shot a bunch of galaxy images under poor seeing conditions and this gives me a better understanding of how to use it. back to processing....

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