What is the precise workflow step that involves blending multiple sequential long-exposure images to create continuous 'star trails' in post-production?

The precise workflow step that involves blending multiple sequential long-exposure images to create continuous 'star trails' in post-production is image stacking using the 'Lighten' blending mode. This technique begins with a series of sequential long-exposure images, which are individual photographs of the night sky captured one after another over a continuous period. Each image, for example, might be a 30-second exposure, showing stars as distinct points or very short streaks, and the full sequence could span an hour or more to capture significant stellar movement. In post-production, these individual images are loaded into image editing software, such as Adobe Photoshop or specialized star trail applications. They are then stacked on top of each other, typically with each image occupying its own layer. The critical step involves applying the 'Lighten' blending mode (also known as 'Maximum' mode in some contexts) to each successive layer relative to the layers beneath it. The 'Lighten' blending mode operates by comparing the pixel values of the active layer with those of the underlying composite. For every single pixel location across the image, this mode selects and displays *only the brightest pixel valuefound among all the layers being compared. Because stars are significantly brighter than the surrounding night sky, as they appear in different positions across the sequential images due to Earth's rotation, the 'Lighten' mode effectively preserves their luminous paths. Any dark sky pixels from a preceding image that are subsequently covered by a star's light in a later image will be replaced by the brighter star's pixels. Conversely, any dark sky pixels from a later image that overlap a star from a previous image will be discarded in favor of the star's brightness. This cumulative process traces the trajectory of each star, combining its bright presence from every image in the sequence into a continuous, glowing line, thereby forming the characteristic star trails.