How Do You Remove Sky Glare or Light Pollution From Your Night Sky Images?

If you enjoy taking pictures of the night sky but live in or near a city, light pollution can really ruin your images. Light pollution often causes an orange glow. Sometimes it manifests as a bright gray background instead of a deep black night sky. This light pollution causes stars and nebulae to fade or, at worst, disappear from view.

Light pollution, or sky glare, is caused by lighting from buildings and street lights at night. It is becoming a worsening problem in urban areas. Many people have never seen the Milky Way because of the amount of glow in the sky.

This step-by-step guide will show you how to remove the effects of light pollution and reveal faint stars from night sky images. It uses free to download GIMP software. This software allows you to modify pictures and images very similar to Photoshop.

How to Remove Light Pollution

The method outlined here will use the despeckle filter tool available in GIMP. This tool removes stars from a copy of your original image. This leaves you only a slightly dirty background. If this copy still contains any nebulae or particularly bright stars, you can remove them using the clone tool. To use the clone tool, select an area of ​​the background sky that doesn’t contain any nebulae or stars right next to the area you want to remove. Select the clean area and then paint the area you want to remove containing the stars. Once you are happy you have removed all details from the duplicate image, then you need to go to the layers dialog and select the mode. Choose to remove it from the drop down box and you will see before your eyes the slightly dirty background will disappear and all the stars will reappear in a beautiful ink black night sky.

The section below provides a step-by-step guide on performing the entire process in GIMP. So install GIMP and follow the instructions below.

1. File > Open and select the image you want to work with.

2. In the Layer dialog, right-click the image and click duplicate layer.

3. Now click on Filters > enhance > despeckle menu.

4. You should now be able to see the despeckle box. Uncheck Adaptive and make sure recursion is unchecked.

5. Set the Radius to 30, Black to -1 and White to 256 and click OK.

6. In the Layer box, make sure the duplicate layer is selected, then click on the mode and choose to remove.

7. Then choose Image > Straighten Image from the menu.

8. Now save your image and show your friends and family amazing images of night sky and constellations.

If you can still see nebulae, galaxies, planets, Milky Way, or bright stars in the image after you clear the speckles, you can remove them using the clone tool. This is outlined above.

Enjoy your newly found clear sky images.

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