Capítulo 2 de 10/4 min de lectura
Finding Polaris
Every observer's first exercise: from the Big Dipper to Polaris.
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Polaris is not the brightest star in the sky, but it is the most useful: it lies almost exactly above the north celestial pole, so it stays still while the whole sky turns around it.
The Big Dipper method
- Find the Big Dipper (seven bright stars shaped like a ladle, in Ursa Major). In spring it is high overhead, in autumn low in the north.
- Pick the two stars on the outer side of the "bowl", opposite the handle: Merak (lower) and Dubhe (upper).
- Extend the line from Merak to Dubhe about five times their separation.
- You reach a fairly bright, isolated star: that is Polaris.
If the Big Dipper is low or hidden, use Cassiopeia, the "W" on the opposite side of Polaris.
A bonus: your latitude
Polaris's altitude above the horizon is roughly equal to your latitude. At about 42° latitude you see it a little more than four fists above the northern horizon.
Polaris is not visible from the southern hemisphere: there, the Southern Cross is used to find south.