Finnish astrophotographer JP Metsavainio published a photograph of the Milky Way taken for 12 years from 2009 to 2021 on his blog.
He explained that the reason why it took so long is the size and depth of individual images. Another reason is that each image was shot in a separate composition and presented as an independent work of art. When combining these pictures, it is necessary to take a picture to compensate for the empty part because the stars may overlap or may create a space. It is said that the color balance and light curve were adjusted by overlapping this photo in Photoshop.
The Milky Way photo, which is a combination of 234 photos taken with 1,250 hours of exposure time in total, contains up to 20 million celestial bodies. Related information can be found here.