IAU constellation drawing atlas
Eridanus constellation
Recognise the shape, know when the whole figure is above your horizon, and practise its 28-segment line map before you step outside.
Observation card
Eridanus at a glance
- Best evening month
- December
- Brightest anchor
- Achernar (magnitude 0.45)
- Whole-figure latitude range
- -90° to 33°
- Declination span
- -57.2° to -3.3°
- Learning map
- 29 plotted stars · 28 segments
- Catalogue lineage
- ptolemy
How to find Eridanus
The complete figure is available from the South Pole northward to about 33° north, favouring southern observers. It is favourably placed during ordinary evening observing hours in December; the exact hour shifts through the month and with longitude.
Achernar, at visual magnitude 0.45, is conspicuous under a reasonably dark sky. Start at the brightest anchor, then compare the direction and spacing of each neighbouring segment. A moonless night and an unobstructed horizon make the fainter links easier.
What this line map means
It belongs to the classical constellation tradition recorded by Ptolemy. Astral Nest uses a simplified IAU learning figure based on Hipparcos star positions, then projects and normalises it so the pattern is easy to trace on screen.
This diagram teaches relative shape, not absolute sky position. Rotation, scale, atmospheric extinction and local obstruction change what you see outdoors, so use a current planetarium or ephemeris for navigation.
Continue the collection
Water collection: Aquarius, Pisces, Cetus, Hydra, Piscis Austrinus, Delphinus, Capricornus