Using "Multiscale high pass" on deep sky images

Image processing, astrometry, photometry, etc.
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Rudi
Posts: 152
Joined: 08 Jan 2019, 04:47

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
Image

NGC4217 before and after MHP
Image

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:
Image

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:
Image

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

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 ;-)
Image

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!
/Rudi

agd.alberto
Posts: 2
Joined: 17 Feb 2019, 08:36

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

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

Rudi, thanks, I experimented. Very well

it344x
Posts: 14
Joined: 02 Feb 2019, 14:00

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.

dredger
Posts: 8
Joined: 31 Jan 2019, 01:47

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.

WD5IKX
Posts: 10
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.

Thanks......now back to processing....
John
CCD-Freak
WD5IKX
Star Ranch Obs - SRO

jauunton
Posts: 12
Joined: 17 May 2021, 04:35

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

Post by jauunton » 06 Jul 2021, 07:37

it344x wrote:
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.
Hi - this can be done -

Mask the area you want to stretch, copy the selected area to a new image, stretch as required, then register the images and merge back to the original using max or blending as you wish. Here is an eg using one of the sample images.

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