Gradient Removal for Blinky PS Elements

[moondog]

I recently posted a widefield image of Orion and Blinky asked me how I got rid of the severe sky glow gradient. I promised to explain the technique. As I used ImagesPlus to process the image and most imagers use Photo Shop, I will describe the technique I've used in PS Elements (3).

Open PS Elements and load the image with the light gradient.

Hold down 'Ctrl' and press 'A' then 'C' then 'V'. This will copy the image into Layer1.

Go to 'Filter', 'Noise' and 'Dust & Scratches' and enter a value of 60 pixels.

Press 'OK' and a blurred image wil be produced. All the stars will vanish in the blur.

At this stage with images with bright stars or a Messier object you may need to blur out any objects with the clone tool that still show through the mask. This wasn't necessary in the image I posted.

Click on the 'Layers pallet' (top right) and change the layer selection from 'Normal' to 'Difference'.

The combined image will go darker and the gradient will vanish.

Use the opacity slider to balance the original and layer 1. Going to '0%' will show the original only. Moving the slider to the right will gradually remove the gradient. On my test image 75% opacity looked best with the background not too dark.

If the image looks OK click the Layer menu and 'Flatten Image'. Save flattened image.

You can then do all the usual stretching, brightening etc to finish the image.

I post below the sub showing the light gradient if you want to have a go.

It is a single non-stacked image of a small size JPEG but it will give you the idea.

MD

[blinky]

Thanks for the guide, I will be sure to give it a try. As soon as these and these disappear.

[richard42]

thats a great way of doing it, there are a few way sthat loose a load of detail bu ti don't think this way does! Well done and thank you very much!!

[moondog]

Glad to be of some help.

This technique also works OK for vignetting in the corners of an image.

MD