• Oct - Octans the Octant

    IAU Constellation

    Size

    50 of 88

    Astronomical Regions

    Intro and Visual description

    Octans the Octant is devoid of bright stars, but three faint stars (not numbered by brightness) make a small triangle.

    The south celestial pole actually lies within Octans. No RA (visible anytime).  

    The nearest easy-to-spot star to the south pole is Beta-Hydri in Hydrus the Little Snake. No brighter star than Achernar (alpha-Eridani) is closer to the south celestial pole, which lies midway between Achernar (Eridanus) and Crux.

  • Bode (1801), Plate 1: Aries Planisphere

    Image

    Uranographia Tab I. Stellatum Hemisphaeri um Arietis

    Bode included two planisphere plates. They are not southern and northern hemispheres; each one has Polaris at the top and the south pole at the bottom. Each one is centered upon an equinox point (where the ecliptic or path of the Sun and the celestial equator intersect). The March equinox point was in Aries in antiquity; by Bode’s time, due to the precession of the equinoxes, it had shifted to Pisces. The September equinox point was in Libra in antiquity; by Bode’s time it had shifted to Virgo.  Bode titled the plates as the Aries and Libra planispheres.

    The Aries planisphere, centered on the March equinox in Pisces, includes these constellations, among others, which appear high overhead in the night skies of autumn:

    Equatorial:  Orion, Taurus, Harpa Georgii, Cetus, Aries, Pisces, Pegasus, Aquarius, Aquila, Scutum.

    Northern:  Auriga, Perseus, Andromeda, Cassiopeia, Draco, Honores Frederici, Cepheus, Cygnus, Lyra.

    Southern:  Eridanus, Apparatus Chemicus, Machina Electrica, Apparatus Sculptoris, Horologium, Toucan, Phoenix, Grus, Indus, Pavo, Tubus Astronomicus, Octans Nautica, Microscopium, Sagittarius, Globus Aerostatic.

    In March, the Aries-Pisces equinox (the center of the Aries planisphere) is traveling with the Sun, rising in the east in the mornings and setting in the west in the evenings. Imagine the center of the planisphere has the Sun pinned to it for that day, and that’s how it would move across the sky. Therefore the constellations near the center of this planisphere are invisible in the daytime sky at that time unless there is a solar eclipse. They would be visible directly opposite the Sun at the September equinox. 

  • Bayer, Uranometria (1661): Southern stars

    Image

    Clockwise from top center: Pavo, Apis, Triangulum Australe, Musca, Chamaeleon, Volans, Dorado, Nubecula Major, Phoenix (left margin), Grus (outside upper left), Indus (left of Pavo), Tucana (below Grus), Hydrus (below Tucana, near center), and Nubecula Minor (just under Hydrus).