Evening Classes Week One How the Sky Moves Presented by Oisín Creaner

Course Outline Week 1: The Sky Week 2: The Planets Week 3: The Stars Week 4: History of Astronomy Week 5: Telescopes Week 6: Deep Sky Objects Week 7: Cosmology Week 8: Alien Worlds

Basic Equipment Your eyes! Binoculars Books Planisphere

Stars & Constellations The Planets (W2) Galaxies & Nebulae (W6) What can I see? Stars & Constellations The Planets (W2) Galaxies & Nebulae (W6) The Moon and Sun (CAREFUL!)

a: Zenith b: Meridian c: Horizon The night sky is like an up-turned bowl above the astronomer’s head. a: Zenith b: Meridian c: Horizon

The Celestial Sphere We can pretend the night sky is a sphere, because all its stars are so far away from us, they don’t appear to move at all.

The Celestial Sphere appears to spin because we see it from the surface of the spinning Earth.

Stars appear fixed on the Celestial Sphere. Polaris Note the positions of – The Plough Polaris Orion The Plough Orion

Celestial Coordinates Declination is equivalent to latitiude and is measured in degrees. Right Ascension is equivalent to longitude and is measured in hours, minutes and seconds.

Special Observation Locations

The View from Athlone - 53° North

Polaris stays in the same place – always directly North, 53° above the horizon.

Where you are on the Earth’s surface determines what constellations you can see, and how often. Declination of stars seen from Athlone Circumpolar – 90° N to 37° N Seen sometimes – 37°N - 37°S Never seen – 37°S - 90°S

The ecliptic is where the Sun is seen against the Celestial Sphere.

The zodiac is a 16º wide band of sky where the planets are seen.

γ The Sun crosses the celestial equator at the first point of Aires, in the constellation Pisces. Ecliptic γ Cel. Equator This is the zero-point of the RA axis (0h 0m)

The Sun’s movement above & below the Celestial Equator The track of the Sun across the Celestial Sphere is known as the Ecliptic.

Precession of the Equinoxes The spinning Earth wobbles on its axis once every 26,000 years.

Using A Planisphere

Polaris Time Date

Match the time with the date

The Sky Window

Autumn Sky- October 10 p.m. Since there are 12 months in the year, and 24 hours in the day, every month, an object will rise 2 hours earlier

Autumn Sky- Andromeda

Autumn Sky- Andromeda

Autumn Sky- Cygnus ‘The Swan’

Autumn Sky- Sagittarius ‘The Teapot’

Orion as a signpost Auriga Gemini Taurus Canis Minor Canis Major

Useful websites www.astronomy.ie/handouts www.stellarium.org Thank You