Observations

Equinox today, Summer is on its way…

A sunset close to equinox from Sydney Observatory and how its position on the horizon changes from day to day

It’s Thursday September 23 today. It is the Spring equinox for the southern hemisphere. And although it’s often said that the length of daytime and nighttime are equal on this day, that is not quite true.

Sunrise is defined to be when the top edge of the Sun first appears above the horizon, and sunset is when the top edge dips below the horizon so there are just a few more minutes of day than night.

Equinox in fact is when the Sun crosses the equator of the celestial sphere, moving (today) from the northern to the southern hemisphere. This happens at precisely 05:21am AEST.

From now until the Summer Solstice our days get longer, and warmer.

Happy Equinox,

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