Why do the constellations disappear from the night sky for a few months?
They disappear when the sun is located in the RA near them, making it impossible to see the stars near the Sun. Each day the Sun travels by about one degree in the sky, that´s about a 4 minute change in right ascension. The sky within about 18° to the East and West is occupied by each sunrise and sunset respectively. That´s about 36°, or over 2 hours in RA, that are hidden by the bright sun, or under 2 months time in a full year. You´d have to see down to both the E and W horizons to catch a star that disappears into the sun after sunset then rises a month or later again before sunrise.
