Dust tool and star reduction

I have DxO PL4 and NIK collection - but I can’t find anything to use for star reduction in astro shots.
The ‘Repair Tool’ is great but I can go removing stars one at a time.
I am hoping there is a tool in this lot somewhere and that I have just not been able to find it yet!
I would like be able to select an area of sky and must the starts in that area so they almost disappear. But just the stars, I don’t want mess with the actual sky between them.

You need something like a median filter but you’re probably going to have to do this in photoshop. It will also remove any fine texture which may make it look fake.

I posted a feature request to automate the frequency separation process which can probably also be used for what you want. But not 100% sure.

Usually people don’t want to remove the stars. They want more stars. :slight_smile:

Hi Spike,

I think doing star reduction of an astroshot with Photolab and/or NIK is not possible.

You’ll need Photoshop or Affinity Photo where you first have to select the stars by luminance, adjust your selection with 1 or 2 pixels and then apply a median or minimum blur filter. The result is less brighter stars.

Another way to do this is using the free application Starnet++. This application is able to get rid of most of the stars and gives you a starless image of your astroshot. You can subtract (blend mode) this starless image from your original image, which will give you an image with only stars.

Then process/adjust the starless and star images separately in layers with Photoshop or Affinity Photo. After your adjustments you blend the starless and star image together.

See a tutorial and explanation of Starnet++ by Nico Carver (Nebula Photos) on Youtube:


Thanks Mike, Lex, for your input - much appreciated.

I’m running DxO and Nix on a Windows VM on my Linux laptop so i’m trying not to use more windows programs than I have to - plus I don’t really want to buy Photoshop.

I shall watch the video later, with interest as Siril, Starnet++ and Gimp will run on my Linux machine.

Hi Spike,

Although Siril accepts RAW files and can develop them, I only use Siril for stacking and background/ gradient removal with TIFF files as input.

I use Photolab for RAW conversion and output to TIFF, only with minimal corrections in Photolab. So no Clearview, no Smart Lightning, et cetera.

I apply the preset ‘no corrections’ and then a subset of the optical corrections and Deep Prime, sometimes a curves adjustment for the offset of the blackpoint as first correction for the light pollution.

I turn off the Lens sharpness as this will introduce a strong halo effect around the stars.

I also turn off the Vignetting control as this can introduce a strange circular banding effect:

see Vignetting filter causing banding - #24 by LexB

But without the correction for Vignetting with Photolab you should do this in another way. Maybe by taking ‘flats’ and use these with Siril.


This is great info! I have a lot to play with and learn. Things like “Lens sharpness” could have taken me weeks to discover on my own :slight_smile:

Hi Spike,

Yes there’s a lot to learn when doing astrophotography. I started 2 years ago and I’m still a beginner and have a lot to learn too. And it’s frustrating to find out that Lens sharpness and Vignetting correction in Photolab is harmful for post-processing astro images.

You can find a lot of information on the internet, but I found it not always helpful and usefull.

But what helped me (and still is helping me today) is the information of Roger Clark on https://clarkvision.com. There’s a lot (!) of information about post-processing of astro images taken with a DSLR on his site under ‘articles’: https://clarkvision.com/articles/index.html

He is using the Adobe Raw Converter or RawTherapee and is explaining the settings he uses. But I think you can also use Photolab with the excellent Deep Prime feature and learn from his settings with ACR.

As I wrote I use Siril (for stacking) and Affinity Photo in combination with Starnet++. But I forgot to mention that I also use the software ‘rnc-color-stretch’ of Roger Clark. It’s also available on Linux, see https://clarkvision.com/articles/astrophotography.software/rnc-color-stretch/

It’s a bit of trial and error to find the correct settings.

This software is command-line driven but on Windows there’s a GUI available.

Be aware that post-processing of astro images is time consuming and sometimes frustrating. But in the end it’s satisfying and fun to do.