The Ulysse Nardin Astrolabium Galileo Galilei, introduced in 1985, is the most complicated one-sided astronomical watch I’ve seen. This very complex instrument indicates the position of the sun and moon, sunrise and sunset, dawn and dusk, moon phases, moonrise and moonset, eclipses of sun and moon, date (approximate), zodiac sign and solar time. Oh, it also tells the current time! 
This watch was the first in what would become Ulysse Nardin’s much-heralded Trilogy of Time. (The “Planetarium Nicolaus Copernicus” was introduced in 1988, and the “Tellurium Johannes Kepler” was introduced in 1992.)
Credit: Ulysse Nardin
Unfortunately, this clockskin doesn’t provide all that astronomical accuracy. It does, however, tell the time. In this clockskin, the serpent serves as a second hand. The current month is displayed in the 12 o’clock position. The sun hand is a 24-hour hand. The moon hand serves as a power meter.
Clockskin Zip File: Astrolabium
A very detailed description of this watch and its history is presented here. (Interpreting much of the astronomical information on the watch dial is quite an exercise!)
If you are interested, my 5-min video of the .watch version of this watch face (which is astronomically accurate) depicts how to interpret most of these astronomical complications. It similarly depicts the other two watches in the Trilogy of Time series.