* The Antikythera Mechanism (circa 100-150 BCE): This complex astronomical device, discovered in 1900, is often cited as the oldest known portable star map. It's technically more of a sophisticated calculator that used gears to predict astronomical events, including planetary positions and eclipses. While it doesn't depict stars directly, it certainly represents an early form of portable astronomical tool.
* The Dura-Europos Synagogue Planisphere (circa 230 CE): This planisphere, discovered in Syria in 1932, is a painted star map on the wall of a synagogue. It depicts a celestial sphere with constellations and might have been used for liturgical purposes. It's not strictly portable, but it's one of the oldest surviving star maps.
* The Planisphere of Bianchini (circa 1280-1300 CE): This planisphere, attributed to Italian astronomer Francesco Bianchini, is a handheld device used for observing and identifying stars. It's a significant example of medieval celestial navigation tools, and its use is documented in historical records.
Other contenders:
* Chinese star charts: There are various star charts from ancient China, including the Dunhuang star chart (circa 649 CE) and the Suzhou star chart (circa 1247 CE). These charts might have been used as portable references, but their portability is uncertain.
* Medieval astrolabes: Astrolabes, invented in the Hellenistic period, became popular instruments for celestial navigation and were used to calculate time and position. Many ancient astrolabes survive to this day, but their specific purpose and usage vary.
It's important to consider that our understanding of ancient astronomical tools is constantly evolving as new discoveries are made. The oldest existing portable star map might still be waiting to be unearthed.
