Naked-Eye Sky Learning 2 (Equator and Tropics)

The equatorial and tropical regions skies are badly known as they never formed a category of their own. Most observers are northerners or southerners, as are the main sky patterns. Equatorial skies are interesting however, as they are a subtle blend of both the northern and the southern skies. Equatorial countries are found all along the equator, in South America, Africa, South-East Asia, and the Pacific

Observational Environment Equatorial Skies Features

Observing

Observational Environment

(note that this section is the same than the one found at "Naked-Eye Sky Learning 1 (Northern Hemisphere)")

Best possible naked-eye sky learning environment is a free 360° horizon. If not, a backyard is useful anyway. Or even a balcony or a simple window. Even if you see less stars and if you have to learn the sky "slice by slice", you will learn anyway. The most important tip is that your eyes progressively get used to the darkness hence progressively see more stars. This is a well known rule of amateur astronomers. Once in a session, just avoid to expose yourself back to any source of light. Should you have to use any documentation as often the case, just use a red flashlight or use the night vision toggle of your planetarium software. Red flashlight are easily found at amateur astronomy retailers or you may easily tweak one: just find a red-tinted bulb, or paint one, or place any convenient red filter on the flashlight. Should you observe from a city or a building, street lamps or other light sources will surely be unwanted sources of light. Just find the appropriate angle which will elude them and just avoid to expose you back to the sources during the observation session

Another point is that you just have to be comfortable while observing. First, you may observe standing, or sitting on a chair or an armchair, at your convenience. On the other hand, always think about how you will get clothed. Observing is always best done in open air (or with a window opened) and some nights may be cold! Dress accordingly and wear appropriate protections like gloves or good shoes, if needed. You have to feel comfortable. In case, just warn your neighbours that should they see a strange shadow with heavy woollen hoods on the head, it's just you learning the sky ;-) A last thing too: should you decide to go to some dark place outdoor to have a better horizon, just think in terms of safety first. Dark places, reasonably, are not the safer places around!

Equatorial Skies Features

Observing

For clarity and use, stars you see in the night sky, are grouped into constellations. Constellations are boundaries inside which a group of stars are seen close together, much of them evoking a figure. In most cases these stars are vastly distant from each other and they are seen forming the constellation figure only by an effect of perspective. As seen from Earth, they are looking like they are close together . Diverse civilizations saw diverse objects, myths or symbols into the skies. The constellations we are using today are mostly due to the Babylonians and Greeks as most of southern contellations were added when discoverers of the 16th century ventured into the southern hemisphere. Definitive constellations boundaries were fixed in 1930 by the International Astronomical Union (IAU). Constellations, for both hemispheres, are at the number of 88. On the other hand, amateur astronomers are used to memorize some alignments which help to find one's way to a constellation or to identify such or such star. At last different parts of the sky are seen along the year due to Earth's revolution along its orbit. It may be assumed that each season comes with its pattern of constellations and stars. All this brings that sky-learning is working along the four seasons. From winter to fall you will learn what constellations are seen in the sky and how to find and identifiy them. Strictly speaking most equatorial countries do not have any delimited seasons like those found in the northern or the southern hemisphere. Temperatures, vegetation, and the length of days are remaining identical all year long! The calendar dates for the four seasons remains useful landmarks however

For any observational purpose, you will have to learn what part of the sky is at your disposal. As a rule of thumb, should you usually see the sun setting, this means that you observation post if facing West. Should you usually see the Sun rising, you are facing East. About midday, Sun is about your North. Hence South is in the opposite direction. A better way to find too is to use a chart, or a compass. Remember that, facing South, you have the celestial equator directly overhead and most of the time, the ecliptic too, which means the planets

Observations tips are given for night's first part, that is about 10:30 p.m. local time. Color maps with Stellarium. Printer-friendly charts with Cartes du Ciel, Patrick Chevalley. The Great Dipper and the Polaris as the Southern Cross and the south celestial pole charts are hand-drawn composites

Caution! A current tendency of the astronomical softwares and charts is to shift from the constellations' shapes as they are usually defined and recognized by the amateur astronomy community. The following color charts on this page are those which are shifting the most in this regard, as the printer-friendly charts are those who do less and are the ones to be used to memorize the basic shapes of the constellations, albeit still not completely accurate. read more!

North, South Winter Sky Spring Sky

Summer Sky Autumn Sky

North, South

Like for northern or southern hemisphere, some developments are useful about the Polaris or the Southern Cross as a mean to locate the north or south celestial pole, not such thing is useful at the equator. The Polaris is just North on the northern horizon as the south celestial pole is just South on the southern horizon. The celestial equator is running overhead East-West. Once this direction verified with a compass or a map, the south celestial pole is just South, on the horizon as the north celestial pole is just North on the horizon

The north pole is further indicated by the Polaris which is literally lying on the horizon -and sometimes below- hence difficult to see.

click to the Great Dipper and the Polaris at the equator

A way to guess where it is is to use the trick used in the northern hemisphere to find it, that is the Great Dipper. At the equator this trick is useful from mid-January to mid-June only as, outside this period, the Great Dipper is not visible for this purpose. The Great Dipper is an asterism, part of the constellation Ursa Major, the Great Bear. The Great Dipper is a quadrilateral at the top left spike of which an arch of 3 stars is extending. The accompanying chart is showing the Great Dipper positions from February, 1st to June, 1st. Once accustomed to the method, you will be able to use it 15 days before and 15 days after. Once the Great Dipper spotted just look for the two stars which makes the outer, righmost edge of the quadrilateral. The Polaris is just at the end of a line extended from these. Strictly, the Polaris is not always visible on the horizon since it is not exactly at the north celestial pole. Hence it has a proper apparent motion. It is not visible, at the observation hours, between mid-April and the end of June. The Polaris is part of the constellation of Ursa Minor, the Litlle Bear, which is better seen like a Little Dipper. The Little Bear itself is not visible between the beginning of September and mid-March

As far as the south celestial pole is concerned, it bears no landmark identical to the Polaris. Southerners are using Crux, the Southern Cross instead. It's an imperfect tool however as the Southern Cross in under the horizon from mid-September to early December. At the equator the Cross is unusable from about July, 8th until February, 1st. Crux, the Southern Cross is a small constellation embedded in the Milky Way. Its shorter axis is wide like both stars either side of Altair. Its main axis is pointing to the south pole

click to Crux, the Southern Cross, showing the south celestial pole (left) and to Canopus as an additional mean to the Southern Cross (right)

The first accompanying chart will help you to find it. On the other hand an additional method is used in the southern hemisphere. It's unavailable too during a part of the year. It's using Canopus (a of Carina, the Ship's Keel). It is one quarter of sky off the Southern Cross, at the same distance from the pole than the latter. Just draw a line from Canopus to the line determined by the Cross' main axis. Where the two lines meets at about an angle of 90°, there fairly is the south pole. Canopus is unavailable to use until April, 8th only

Winter Sky

In winter the show is South-southeast. All the southeastern part of the sky is filled by the bright stars of the constellations born from a large, ancient constellation, Argo, the Ship, as Orion is at the zenith. Starting at the horizon, Carina, the Ship's Keel, Vela, the Ship's Sails, and Puppis, the Ship's Stern are the three constellations which were created about 1750 to replace Argo, the Ship, which was the ship of the Argonauts journeying in search of the Golden Fleece.

click to winter's southern horizon. retrieve a printer-friendly chart

The three constellations are embedded into the Milky Way as the bright Canopus is seen right of the flow of bright stars. Atop the flow, high, another bright star is seen. It's Sirius, main star of Canis Major, the Great Dog. Canis Major, the Great Dog, itself is fine. Here, you are about the zenith where the famous constellation of Orion is lying. Straight up, overhead, here is this quadrilateral, with a line of three stars pointing to the East. It's Orion, the Hunter. The three stars are the Orion's Belt with the Orion Nebula below them. Left of Orion, the other bright star is Procyon, of Canis Minor, the Little Dog

Now turn East. Here is Procyon again, high in the sky, with another quadrilateral, left of it. It's Gemini, the Twins, with Castor and Pollux. Lower, the sky is less dense. The faint chain of Hydra, the Hydra, is starting below Procyon and heading to the horizon as Cancer, the Crab, is bottom right of Gemini, the Twins. Cancer, the Crab, is home to a fine open cluster, M44 (Praesepe, the Beehive), which is easily visible, just near the two faint, central, stars of the constellation. Another interesting figure East is Leo, the Lion, which is not entirely risen above the horizon. The typical Sickle of the Lion -this asterism in form of a sickle, including Regulus- is already well visible
Should you turn West you will first follow the famous Eridanus, the River Eridanus, a long chain of stars starting at Rigel, one star of Orion, and meandering a long way down to a bright star. This is Achernar. On the other hand see Cetus, the Whale, which is found at the first bent of the River. At last, northwest, look at Taurus, the Bull. Its brightest star, Aldebaran, is included in a loose, V-shaped, open cluster which are the Hyades. The constellation of Perseus is lower. Aries, the Ram, and Triangulum, the Triangle, are in the neighbourhood as Pisces, the Fishes, and Andromeda are partially seen only. Lower than Aldebaran, spot a little, obvious, group of stars. These are the famous Pleiades

click to winter's eastern horizon (left) and western horizon (right). retrieve printer-friendly charts (eastern horizon, western horizon)

Spring Sky

In spring the show is clearly South. Turn South! From Scorpius, the Scorpion, in the southeast to Canis Major, the Great Dog, in the southwest, it's the typical southern hemisphere band of constellations embedded into the Milky Way which is lying above the horizon. A step above the whole the faint Hydra, the Hydra, is seen. Let's begin with the embedded constellations. Scorpius, the Scorpion, S-shaped with the bright Antares preceded by an arch of stars, is followed by Lupus, the Wolf. Further, two bright stars are found. These are Alpha Centauri and Agena. These two stars are together known as the Pointers. The line which joins Alpha Centauri to Agena is "pointing" to Crux, the Southern Cross. This is easy to remind like "Alpha, Beta, and the Cross" (ABC). Alpha Centauri is the famed Alpha Centauri, that is the star which is nearest to us. This is more precisely a system of three stars as one of it, called "Proxima Centauri", is our nearest neighbour, at about 4.35 light-years. Its proximity relative to the other two is due to its huge orbit. Next is found Crux, the Southern Cross, with the typical "Coalsack" left of the spike. The "Coalsack" is a dark interstellar cloud. Between the Southern Cross, down to about Canis Major, the Great Dog where Sirius is lying, you will find back these constellations which were created from Argo, the Ship. Carina, the Ship's Keel, with the bright Canopus (low), Vela, the Ship's Sails, and Puppis, the Ship's Stern. Another marvel of the southern skies is seen here: Omega Centauri (NGC 5139), a globular cluster shining at mag 3.7 top left of the Southern Cross. It is found on the line Agena-e Centauri, a little less than the distance between the two stars. See too the famous False Cross, which is a group of stars looking like a larger but fainter cross. At last, a row above, near the zenith, see the fine, faint, long, chain of Hydra, the Hydra, along which Corvus, the Crow, Crater, the Cup, and Sextans, the Sextant, are anchored

click to spring southern horizon (the southern embedded constellations in the Milky Way) (left) and to Omega Centauri, the False Cross (right). retrieve printer-friendly charts (southern embedded constellations in the Milky Way, Omega Centauri, the False Cross)

West, where Hydra, the Hydra, ends, some of the constellations you saw in winter are found back. Right beneath the head of Hydra, the Hydra, Procyon, of Canis Minor, the Little Dog, with Gemini, the Twins, to its right. Cancer, the Crab, with the open cluster M44 (Praesepe, the Beehive), and Leo, the Lion, high in the sky. On the eastern horizon, the Great Dipper is pointing to Arcturus, then to Spica. "Arc to Arcturus, speed on to Spica." Arcturus is the main star of Bootes, the Herdsman, as Spica of Virgo, the Virgin. Both stars are found by extending the arch of stars of the Great Dipper. Ophiuchus, the Serpent Holder, is still low on the horizon as one of its Serpents is above it. The little fine constellation left of the Serpent is Corona Borealis, the Northern Crown

click to spring western horizon (left) and to spring eastern horizon (right). retrieve printer-friendly charts (western horizon, eastern horizon)

Summer Sky

In summer, the sky is the reverse of the winter sky, that is that the embedded southern constellations in the Milky Way are seen South-southwest, from Crux, the Southern Cross, to Scorpius, the Scorpion. The Cross is just above the horizon with the Pointers above it, providing a fine show as Lupus, the Wolf, and Scorpius, the Scorpion, are following up higher in the sky. On the other hand, Sagittarius-Scorpius region is marking the center of our Milky Way Galaxy. It's there that the bulge of the Galaxy is found, filled with old, yellow stars, as is the supermassive black hole which is found lying at the center or our universe-island like in any other galaxy. South of Sagittarius, the Archer, look at the small Corono Austrina, the Southern Crown as all the southeastern part of the sky is filled with typical southern constellations like Microscopium, the Microscope, Indus, the Indian, Pavo, the Peacok, or Grus, the Crane. Capricornus, the Goat, is high as the bright star Fomalhaut, of Piscis Austrinus, the Southern Fish, is low

click to summer southern horizon. retrieve a printer-friendly chart

Aquarius, the Water Bearer, is lying low on the horizon as a well-known figure of the northern summer sky, the summer triangle, is high northeast. The summer triangle is the triangle formed by three bright stars, Deneb, Vega, and Altair. Deneb is the main star of Cygnus, the Swan. Vega belongs to Lyra, the Lyre, as Altair is the bright star of Aquila, the Eagle. Some fine small constellations are seen in the neighbourhood like Sagitta, the Arrow, Delphinus, the Dolphin, or Equuleus, the Little Horse. West the weird arch of stars of the Great Dipper, isolated from the asterism which is hidden under the horizon, is always pointing to Arcturus and Spica, as, although high, Ophiuchus, the Serpent Holder, the Serpents, and Hercules are fine targets. Ophiuchus, the Serpent Holder, is Asclepios the Greek god of medicine who was put into the sky like a constellation as the two Serpents (one each side of Ophiuchus) are the serpents the doctors then used like herb-finders. Hercules is fine too and home to the famous globular cluster M13. M13 is located on the lower side of the central quadrilateral (which is named the "Keystone") at one third of the length of the side from the right

click to summer eastern horizon (left) and to western horizon (right). retrieve printer-friendly charts (eastern horizon, western horizon)

Autumn Sky

The fall sky should be better seen like an ensemble of sky patches of interest. The eastern horizon is interesting as Orion, the Hunter, is just lying on the horizon as Eridanus, the River Eridanus, is leaving Rigel and meandering until Achernar, South. Cetus, the Whale, is above the first bent of the River. Northeast are seen Perseus, with its brightest star, Algol as Aldebaran, of Taurus, the Bull, is seen too, along with Capella the bright star of Auriga, the Charioteer, low northeast. The southern horizon is peppered with various typical southern constellations. Achernar, Fomalhaut (Piscus Austrinus) or Alnair of Grus, the Crane, are well visible as Caelum, the Chisel, Reticulum, the Reticle, Tucana, the Toucan, or Indus, the Indian, are seen. West, it's the summer triangle which is found back although low northwest (Deneb of Cygnus, the Swan, Altair of Aquila, the Eagle, and Vega of Lyra, the Lyre) as Capricornus, the Goat, Aquarius, the Water Bearer, are high and well visible. At last, have a look high, northwest. It's the best season to see, although they are high, the Great Square of Pegasus, Andromeda, and Pisces, the Fishes. Andromeda is home to the famous M31 galaxy. M31 is an image of what our own Milky Way Galaxy would look might we see it from the outside. M31 is easily found. Spot the second bright star of Andromeda starting at the spike of the Great Square, spot a fainter star beneath it, a fainter still beneath and right. M31 is there

click to fall eastern horizon (top left), southern horizon (top right), western horizon (bottom left), and the Great Square of Pegasus, Andromeda, M31 (bottom right). retrieve printer-friendly charts (eastern horizon (top left), southern horizon (top right), western horizon (bottom left), and the Great Square of Pegasus, Andromeda, M31)

Conclusion

Here we are! You now have learned how the equatorial regions are not only about northern and southern skies but are a subtle blend of both. From there most usual figures of the northern skies like Leo, the Lion or Orion are seen high at the zenith as, on the other hand, it's obvious that along three seasons in a row, the southern horizon offers remarkable views of the southern hemisphere sky. You may consider you just entered the amateur astronomers community of the equatorial regions! Should you feel that some parts of the sky are still badly understood, do not hesitate to come back to some parts of this page and to deepen your skills. On the other hand, each month, on this site, at the "Monthly Sky" section, you will find a view of the monthly western and eastern horizons. This will provide you with further insights as other tutorials about observation or about theory are helpful too