Hydra

When and where to look for Hydra

Hydra crosses the meridian — its highest point in the sky — at local midnight around February, which makes the months from January to March the easiest time to find it in the evening. It spans declinations -33.9° to +6.4°, so best from the southern hemisphere; it rises for observers between about 84°S and 56°N.

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

Brightest stars in Hydra

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

What Hydra is made of

The catalogue lists 243 stars within Hydra, of which 243 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 HD 100623 at 31.2 light years. The most distant is HD 72561 at roughly 1,647 light years — stars that appear side by side here are nothing of the sort.