Astronomy is the scientific study of celestial objects. Stars, planets, comets, nebulae, star clusters and galaxies.
It is a natural science astronomy – the study of these objects – and astrophysics is the study of their behaviour.
Prehistoric cultures like those at Stonehenge made the place an astronomical artefact but it wasn’t until the telescope that helped astronomy develop into a modern science. It is one of the few sciences where amateurs can play an active role. “Astro” means star and “nomy” means law in Greek.
Beginning as a measurement of time for crop planting purposes, astronomy was done from vantage points like high ground in order to map the stars.
Galileo’s sketches of the moon were the first to show its surface was actually mountainous and Newton’s laws explained the motion of the planets. With his telescopes Newton discovered Jupiter’s moons.
The Milky Way is Earth’s galaxy and the sky is free for us all to see with binoculars the most common instrument used in astronomy. Amateurs star gaze while professionals use computers in the office.
Some stars orbit in pairs, others differ in brightness. Jupiter has a black spot, which is the shadow of its moon and the Great Red Spot. Our moon has mountains and craters.
Most telescopes are refracting telescopes with a large lens at the front and a smaller one near the eye while reflecting telescopes use mirrors.
Greek astronomer Ptolemy thought the Sun, the Moon and the Planets and Stars all revolved around the Earth.
Stars are moving though they appear to be stationary. Foucault’s pendulum experiment proves that the swinging weight changes path and the Earth behaves in a similar manner.
Orion is a group of seven stars like four points of a square with three in the middle and by midwinter the Sun appears opposite Orion in the sky and the constellation is well placed for midnight viewing.
Our star is the Sun and has always been used as the basic timekeeper. On most sundials the gnomon that casts the shadow is parallel to the Earth’s axis and the difference between GMT and sundial time and Apparent Solar Time is known as the equation of time.
If you plant a stick in the ground its shadow will point exactly north (or south in the southern hemisphere) at noon and if you mark the points every day it forms the analemma and to make a proper sundial you need the latitude of your location to angle the gnomon – I used a chopstick when I did it in Seoul and they are at 37 degrees latitude.
