🔍 Key Concepts

• The phase of the Moon determines its position relative to the Sun in the sky • A last quarter Moon is 90° west of the Sun in celestial longitude (about 6 hours of right ascension behind the Sun) • Think about the local time relationship between when the Sun is highest, rising, or setting and where a last quarter Moon would be on the opposite side of the sky

💭 Think About

• Picture the Moon-Earth-Sun line for a last quarter Moon: where is the Sun in the sky when the last quarter Moon is on your local meridian (due south or north)? • If the Sun crosses the meridian at about 1200 LMT (noon), about what local times will a body that is 6 hours behind the Sun cross the meridian, rise, and set? • Compare the rise time of the last quarter Moon to the familiar times for the first quarter Moon and full Moon—how do they shift by about 6 hours from each other?

✅ Before You Answer

• Be clear on the geometric definition of a last quarter Moon (Moon-Sun angle as seen from Earth) • Use the rule of thumb: each 90° difference in celestial longitude is about 6 hours of time difference in the sky • Check whether the time you pick would place the Moon roughly opposite, ahead of, or behind the Sun in the daily path across the sky in a way consistent with "last quarter"