All tools
Planetary Configurations Simulator
NAAP configurations: inner planets show conjunctions and greatest elongation; outer planets show opposition and quadrature. Mercury–Sun and Venus–Sun presets included.
Before you start
Planets line up with the Sun in named ways: conjunction, opposition, elongation. This NAAP lab uses Mercury–Sun, Venus–Sun, and bright outer-planet examples.
Key idea
Inner planets never appear opposite the Sun. Outer planets are brightest at opposition, when Earth sits between them and the Sun.
What you see
- Sun at the centre with Earth on a blue orbit
- Presets for Mercury, Venus, Mars, Jupiter, Saturn
- Elongation angle in degrees
Try this
- Compare Mercury–Sun vs Venus–Sun greatest elongation
- Switch to Mars opposition — that is when Mars is due south at midnight
- From Hong Kong, opposition planets transit high in the south
Why it matters in Hong Kong
Venus is often the bright evening or morning ‘star’ over Victoria Harbour; Mercury is harder and stays near twilight.
Common mistakes
- Expecting Venus at midnight — it never strays far from the Sun
- Mixing up inferior and superior conjunction
Glossary
- Elongation
- Angle at Earth between the Sun and a planet.
- Opposition
- Outer planet opposite the Sun in the sky.