天文入门指南
在星空中辨认方向、了解宇宙的第一步：无需器材，今晚就能开始。
共 10 章，总阅读时间约 47 分钟
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Cardinal points, height above the horizon and how to measure the sky with your hand.
阅读约 5 分钟
Why stars rise and set, and why constellations change with the seasons.
阅读约 5 分钟
Its phases, when to observe it and why the full Moon is not the best time.
阅读约 5 分钟
Which ones to learn first, season by season, from the northern hemisphere.
阅读约 6 分钟
Letting your eyes adapt to the dark and choosing the right place and night.
阅读约 4 分钟
What to start with and what to look for when buying your first instrument.
阅读约 6 分钟
Recognising what moves across the sky and sending a good report.
阅读约 5 分钟
术语表
最常遇到的术语，一句话解释。
- Magnitude
- A measure of apparent brightness: the lower the number, the brighter the object. Sirius is −1.5; from a dark sky the naked eye reaches about +6.
- Zenith
- The point in the sky straight above your head.
- Azimuth
- Direction along the horizon, measured in degrees from north through east (east = 90°, south = 180°).
- Ecliptic
- The path the Sun follows across the sky during the year; the Moon and planets stay close to it.
- Astronomical unit (AU)
- The mean Earth–Sun distance: about 149.6 million km.
- Light-year
- The distance light travels in a year: about 9.46 trillion km. It is a distance, not a time.
- Opposition
- When an outer planet is on the opposite side of Earth from the Sun: it is up all night and at its brightest.
- Conjunction
- When two objects appear close together in the sky as seen from Earth; in space they can be very far apart.
- Elongation
- A planet's angular distance from the Sun. For Mercury and Venus, greatest elongation is the best time to observe them.
- Radiant
- The point in the sky from which a shower's meteors appear to come; it names the shower (Perseids from Perseus).
- ZHR
- Zenithal Hourly Rate: the theoretical number of meteors per hour under a perfect sky with the radiant overhead. In practice you see fewer.
- Terminator
- The line separating the lit and dark parts of a planet or the Moon.