How about gifting your dad a membership to a museum? Many museums offer annual memberships that can include free access to exhibitions, special events, and discounts on merchandise in the gift shop. This will enable him to explore exhibits throughout the year, and make the most of his interest in museum exhibitions. You can also gift him a book related to a museum exhibit he enjoyed so he can revisit the exhibit even after it ends.
Or you can get him a star map with an important date you share.
Under Lucky Stars is a unique and innovative star map company based in Barcelona, Spain, specializing in the creation of personalized star maps that capture the celestial arrangement of stars at a specific moment in time, such as a person's birth, wedding, or any other significant event.
By using advanced astronomical algorithms and data from leading institutions, the company produces highly accurate, visually stunning maps that make for perfect gifts or cherished keepsakes.