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Originally Posted by g__day
Maybe, thanks. So do the Sun and Moon raise and set at the same spot on the horizon, and reach the same maxium altitude from the horizon every day of the year?
I just assumed over six months you'd see the Sun, moon and stars describe alot shallower arcs in Winter months - is this optical illusion alone?
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The plane of the Earth’s equator is at an angle of 23.5 deg to the plane of the Ecliptic (Earth-Sun plane).
This means (approximately and simplistically) that in the Southern Hemisphere:
- Mid-Summer (21 Dec) – the Sun rises 23.5 degrees S of E (Summer Solstice)
- Mid-Spring (21 Sep) – the Sun rises in the E (Spring Equinox)
- Mid-Winter (21 Jun) – the Sun rises 23.5 degrees N of E (Winter Solstice)
- Mid-Autumn (21 Mar) – the Sun rises in the E (Autumnal Equinox)
Based on Brisbane’s southerly latitude of 27.5 deg
- At the Summer solstice the Sun is approx 86 deg above the horizon at mid day.
- At the equinoxes the Sun is approx 62.5 degrees above the horizon at mid day.
- At the winter solstice the Sun is approx 39 deg above the horizon at mid day.
Cheers
Dennis
PS - Solstices and Spring and Autumnal Equinoxes reversed from standard N hemisphere centric perspective.
Edit 2 - added some calcs as follows:
At Brisbane’s latitude of 27.5 deg S, the celestial equator is inclined at 62.5 deg to the horizon. Therefore;
- When the Earth-Sun plane (Ecliptic) is 23.5 deg “above” the celestial equator, this puts the Sun at 62.5 + 23.5 deg above the horizon = 86 deg.
- When the Earth-Sun plane (Ecliptic) is 23.5 deg “below” the celestial equator, this puts the Sun at 62.5 - 23.5 deg above the horizon = 39 deg.
- Where the Ecliptic intersects the celestial equator at the two equinoxes, then the Sun will be at 62.5 degrees above the horizon.