The difference comes from the number of stars shown on each of the three night sky poster sizes.
The large size is twice as big as the medium size star map, and the medium size is twice as big as the small size. Due to medium and small size being smaller, it's harder to show the smaller stars on them. Therefore, the large size star map will have the highest accuracy with most stars shown as compared to Medium and Small posters.
All posters are printed on same quality paper using the same printers and going through the same strict quality assurance process! Go to our Star Map Builder to find the right poster size for you!