I used the same Photoshop technique in my sketch of the Oyster Nebula as I did for NGC 1502. In this instance, the “Radius” and “Threshold” adjustments improved the soft appearance of NGC 1501. However, if you wish to leave the nebula untouched and only soften the stars around it, you need to add a mask to the duplicated layer. To achieve this, click on the “Add a layer mask” icon in the “Layers” panel. You can then use the “Brush” tool to remove the nebula from the duplicated sketch and expose the original version below.
Questions or suggestions? Please feel free to contact me at
erikarix1@gmail.com.