The Sky at Night
From DQWiki
(These are notes for a proposed page on Alusian naked eye astronomy)
| Table of contents |
Stars
Brightnesses
A star's brilliance is measured by it's magnitude. Each successive magnitude is 2.5 times fainter than the one before it. The average human can see down to magnitude six in a clear and moonless night in the country, away from any other light sources. Magnitude one is defined as being 100 times brighter than magnitude six, and a few stars are brighter than that.
- Sun -37
- Full moon -12
- Freya -5 (at max)
- Thunor -3 (during opposition)
- Wotan -3 (during opposition)
- Ariel -2 (at max)
- Hela 0 (during opposition)
- Merlyn 5 (when visible)
- Sirius -1 (From Greek Seirius - spot the Demon!)
- Next Five Brightest Stars 0
- Next Ten Brightest Stars -1
Circumpolar
Some stars are circumpolar, i.e. they never rise or set, being always visible in the sky. Instead they seem to scribe a circle around a point in the sky called the North Celestial Pole (or the South Celestial Pole in the Southern Hemisphere). The height of the Pole above the horizon and the number of stars that are circumpolar is defined by the observer's latitude. There is a bright star located near the North Celestial Pole but the South Pole has no such visual aid.
Constellations
Stars are arranged in groupings called Constellations, and the exact number and groupings depend on which society mapped the heavens.
Zodiacal constellations
These are the fourteen constellations that the sun, moon, and planets wander through in their path through the sky. In order from the ascending node (where the ecliptic crosses the celestial equator) they are (using the Western Kingdom maps): Maiden, Messenger, Smith, Thief, Lover, Warrior, King, Mother, Magician, Wolf, Void, Reaper, Fool, Farmer.
Other noteworthy constellations
In the Southern sky, there is a constellation called Michael's Sword, although many sailors refer to it as the Cross, which can be used to help find the South Celestial Pole. A grouping called the Wains helps find the North Celestial Pole.
Wanderers
As well as the fixed stars, there are six other bodies (not counting the Sun and the Moon) that move in the heavens. They all follow a path near the ecliptic (the yearly path that the sun takes through the sky). They are: Ariel, Freya, Thunor, Wotan, Hela, and Merlyn.
Both Ariel and Freya appear either in the eastern sky near morning, or the western sky at evening. Ariel is hard to see as it is always close to the Sun and is usually drowned in the latter's glare. Freya however, is the brightest object in the night sky (excepting the Moon) and is unmistakable. The best time to see them is when they are at greatest elongation from the Sun.
The other four can be at any angle from the Sun and are usually brightest when they are at opposition, i.e. 180 degrees from the sun. Merlyn is hard to see at the best of times since it is so faint but the others can be picked out easily, Thunor especially since it has a reddish hue.
Occasionally these four can be seen to move backwards in the sky. This is called retrograde motion and several theories have been put forward to explain it. It usually occurs around opposition.
