Location – The planets always travel within a few
degrees of the path of the Sun. The path that the Sun appears to travel against the sky is called the ecliptic. It marks the
centre of the band of sky within which the Moon and planets are found. This area is known as the zodiac. The ecliptic passes
through the 13 zodiacal constellations of Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Ophiuchus,
Sagittarius, Capricorn and Aquarius. Ophiuchus (The Serpent Bearer) does not appear in the astrologer's zodiac although the
planets spend more time in it than in Scorpio.
Astrologers use a different zodiac from astronomers for reasons of precession. The Earth moves on its axis with a wobbling
motion like a spinning top, the axis tilted away from the vertical by 23.5 degrees. Whereas the axis of a top takes only a
few seconds to complete its reeling movement, the period for the earth is 25,800 years. This movement, known as precession,
causes slow changes in which constellations make up the zodiac. Astronomers use the real time zodiac, whereas astrologers
use the zodiac of more than 2,000 years ago.
Location is a big clue as to whether you might be observing a planet (or not). If you know where the Sun and Moon rise and
set you can follow this line across the sky, night or day, and observe the planets in our Solar System following a similar
Brightness - Some of the planets quite simply appear too bright to be stars. Venus, the brightest
planet, is an example. It is never far away from the Sun in the sky, so whenever an extremely bright object appears in the
sky towards the west after sunset, or in the morning towards the east before sunrise, most probably it is Venus.
As an evening object, Venus is often the first bright object visible, before any stars appear in the sky. Mercury also
appears in areas of the sky around sunrise and sunset, but never looks as bright as Venus nor is as far from the Sun as
Venus. Mercury appears only during twilight, and Venus never remains visible through the night. Whenever a very bright
yellowish white point of light appears in the sky in the middle of the night, it is probably Jupiter. Unlike Mercury and
Venus, Jupiter is not always near the Sun in the sky and can appear high in the sky at midnight. Mars and Saturn can also
appear far from the sun in the sky, rising well after sunset. Mars rarely outshines Jupiter and the brightness of Saturn
never equals that of Jupiter or Venus. Mars can often be distinguished by the fact that it has a slight but distinct reddish
or orange colour. Saturn, on the other hand, appears to be yellowish. The other planets are too faint to be seen with the
Twinkling – As per the nursery rhythm, stars twinkle. Planets, however, usually seem to shine
steadily. Twinkling is an effect of turbulence in the Earth's atmosphere whereby starlight passing through the atmosphere
shows the intensity to vary slightly but rapidly. Observations with a telescope reveal that a star appears to slightly move
about. The reason why stars twinkle and planets do not is that stars are so far away that they look like points of light
even when viewed through large telescopes but planets are close enough to Earth to be seen as a disc by telescopic image.
The light from different parts of a planet's disk averages out and makes a planet appear relatively steady in both
brightness and position. Planets may seem to twinkle if the atmosphere is especially turbulent, or if an object is low in
the sky (observed through large amounts of atmosphere). Under these conditions, an object may seem to change in colour
- i.e. when Venus is low in the western sky it can change from a greenish hue to a reddish hue and back again.