• Big Dipper

    Asterism Visual Appearance

    The Big Dipper is one of the most easily recognizable groups of stars in the sky. It is referred to as circumpolar because, for most northern observers, it never completely sets below the horizon, but is visible in northern skies year-round.

    The Big and Little Dippers pour into each other, just as the Big Bear and the Little Bear ceaselessly turn around and around the northern sky. The Guard stars of the Little Dipper protect Polaris from the Great Bear, just in case he might try to catch the North Star for himself.

    Three stars make up the Big Dipper’s handle, and four stars make its bowl. If you can find the Big Dipper in the sky, you have a skymark to orient yourself both on the Earth and in the Heavens. The two stars that form the pouring side of the bowl point to Polaris, the north star. Polaris is a rather faint star about five times farther away than the distance between the pointers themselves, and marks the tip of the handle of the Little Dipper.

    Use the Big Dipper to find your way around the night sky.

    Asterism Skylore

    What Americans know as the Big Dipper has many names, being variously called the "Drinking Gourd" (America), "Plough" (Britain), "Wagon" (Europe), among many other names.

    In Middle Earth, the Big Dipper (or possible Ursa Major) was known as Valacirca (the Sickle of the Valar), and Cerch im(b)elain (Seven Butterflies). (Rachel Folmar)

  • The Horse and Rider

    Asterism Visual Appearance

    Look at the second star from the end of the dipper’s handle. Look closely, and you may see two stars, Alcor and Mizar (Migh-zar), which are also known as the Horse and Rider. According to the Greeks, the second star is one of the Pleiades sisters, who left her six sisters in the constellation Taurus (TORE-us) when she married. Mizar, the brightest of the two, is visible as a double star in a large telescope. Interestingly, from spectroscopic evidence it is known that both components of Mizar are each double stars as well, so that there are actually four stars in Mizar, which along with Alcor make five stars in this single system.

  • Bode (1801), plate 2: Libra Planisphere

    Bode-1801-02-planisphere

    Uranographia Tab II. Stellatum Hemisphaeri um Librae. 

    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 Libra planisphere, centered on the September equinox in Virgo, includes these constellations, among others, which appear high overhead in the night skies of spring:

    Equatorial:  Ophiuchus, Serpens, Libra, Virgo, Crater, Corvis, Hydra, Sextans, Leo, Cancer, Monoceros.

    Northern:  Hercules, Quadrans Muralis, Bootes, Canes Venatici, Ursa Major, Telescopium Herschelii, Gemini, Lynx, Ursa Minor.

    Southern:  Scorpius, Tubus Astronomicus, Lupus, Centaurus, Apis, Chameleon, Crux, Argo Navis, Robur Caroli II, Circinus (sector compass), Canis Major, Pixis Nautica (magnetic compass), Machina Pneumatica (air pump), Officina Typographica (printing press).

    In September, the Libra-Virgo equinox (the center of the Libra plate) is traveling with the Sun, rising in the east in the morning and setting in the west in the evening.  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 March equinox.