Cassiopeia

When and where to look for Cassiopeia

Cassiopeia crosses the meridian — its highest point in the sky — at local midnight around September, which makes the months from August to October the easiest time to find it in the evening. It spans declinations +56.5° to +63.7°, so visible from everywhere north of about 26°S.

The quickest way to find it is to open the live AR sky map and point your phone at the sky — if Cassiopeia is above your horizon right now, its figure is drawn in the position it genuinely occupies above you.

Brightest stars in Cassiopeia

Magnitude runs backwards: lower numbers are brighter, and anything below about 6.5 is beyond the naked eye under a dark sky.

What Cassiopeia is made of

The catalogue lists 160 stars within Cassiopeia, of which 160 are magnitude 6.5 or brighter — the limit of what an unaided eye picks up under a genuinely dark sky. The rest need binoculars or a telescope.

Spectral make-up

Spectral class is a temperature ordering, running from O at around 30,000 K down to M below 3,500 K. A constellation is a direction, not a group, so this is simply what happens to lie along that line of sight.

The closest catalogued star in this direction is Achird at 19.4 light years. The most distant is HD 224893 at roughly 3,077 light years — stars that appear side by side here are nothing of the sort.