Some galaxies have bright cores and we often publish images with the bright core intact, however, you can apply an adjustment that reduces the tone of the core making it less bright and bring out more detail.

This tutorial walks you through toning down the core of a bright galaxy using GIMP 2.10 or later.

The Result

The following is an image highlighting the bright core of galaxy NGC 2903:

The center is quite bright and there’s little detail in it. This is the result after applying an adjustment using GIMP:

The center is not as bright and some detail is apparent.

Making The Adjustment

1. Open an image of a bright galaxy or save the ‘before’ image from this article

 2. (this is optional but might help you see the effect) Duplicate the background layer

3. From the menu, select Colors – Shadows-Highlights

4. Fill in the form as follows:

Shadows: 0

Shadows color adjustment: 0

Highlights: -100

Highlights color adjustment: 0

White point adjustment: 0

Radius: 15

Compress: 50

5. Click Ok to commit the adjustment

6. Apply the same adjustment a second time, filling in the form the same way

You may have to adjust the Radius parameter a little based on the size of the bright center – your goal is to achieve a balance between reducing the bright core and the transition to the rest of the galaxy – you want the transition to look natural.

Conclusion

 In this walk-through, you learned how to apply a Shadows-Highlights adjustment to tone down the core of a bright galaxy.