To put it simply, a fall constellation is just a constellation. A constellation itself is a group of stars that form a pattern that are usually named after the form astronomers believe it takes or a mythological character. (Modern astronomers have found 88 constellations. However, only 13 of them are fall constellations.)
Autumn, or fall, constellations appear "between 0 hours and 6 hours of Right Ascension." Right Ascension is the angular distance measured toward the East olong the celestial equator from the vernal equinox to the hour circle. It is almost the same thing as terrestrial (Earth's) longitude, save for the fact that it's celestial (in outer space).
This photo shows Right Ascension. Source: HaikuDeck images
Autumn, or fall, constellations appear "between 0 hours and 6 hours of Right Ascension." Right Ascension is the angular distance measured toward the East olong the celestial equator from the vernal equinox to the hour circle. It is almost the same thing as terrestrial (Earth's) longitude, save for the fact that it's celestial (in outer space).
Constellations are always at their most visible at nighttime. Given their name, fall constellations specifically are at their most visible during autumn.
Among the fall constellations is the constellation “Andromeda." The constellation is named after the wife of Perseus of Greek Mythology, who was chained to a rocky edge of the sea as a sacrifice to Poseidon, Greek god of the sea. It contains many galaxies.