(Continued from page 5)

• Setting times for the sun, moon and planets in your sky
• In the Southern Hemisphere, the steepness of the ecliptic causes the moon and planets to stay out longer after sunset
• In the Southern Hemisphere, it's a totally different story. Given clear skies and an unobstructed horizon, people at southerly latitudes can view tonight's moon and Spica without much difficultly. The moon and Spica - and the planets Saturn and Mars - all set much later after sunset in the Southern Hemisphere.
• Why the stark difference between the Northern and Southern Hemispheres? It's because the tilt of ecliptic - the pathway of the sun, moon and planets - reaches an extreme as the sun sets around the time of an equinox.
• What is the ecliptic?
• At sunset on the autumn equinox, the ecliptic makes its shallowest angle with the horizon for the year - so any young evening crescent around the time of the autumn equinox lurks close to the horizon at sunset and sets very shortly thereafter. The September equinox, by the way, is the Northern Hemisphere's autumn equinox.
• In the Southern Hemisphere, the September equinox is the spring equinox. At sunset on the spring equinox, the ecliptic intersects the horizon at its steepest angle for the year - so any young evening crescent around the time of the spring equinox stands high above the setting sun, and sets a maximum time after sundown.
• If you miss the young moon after sunset this evening, try again tomorrow, as the moon displays a larger crescent and sets later after the sun.
•
•