University Lowbrow Astronomers

University Lowbrow Astronomers
Introduction to the Constellations

by Dave Snyder
Written: December, 2003

This page is for beginning amateur astronomers who are still learning how to identify constellations.  It is designed for observers at about 40 degrees north latitude (though it will work for latitudes somewhat north or south of that).

There are four different charts, you should select a chart based on the time of year, and whether you are observing before midnight (the evening) or after midnight (the morning). It describes major “landmarks” in the night sky and how to use those landmarks to find other constellations.

If you live in city or a suburban environment, you probably will encounter light pollution.  Light pollution will prevent you from seeing all of the stars shown in these charts; you can see the brighter stars, but you will not see the fainter stars.  Your ability to see fainter stars will improve if you can find a location away from bright lights and if you are patient: your ability to see faint sees will improve if you allow your eyes to adjust to the darkness for a half hour or more.

You may need to find a location away from obstructions like trees, buildings and mountains.

Spring Evenings & Winter Mornings

The Big Dipper

The stars of the Big Dipper are circumpolar from northern latitudes (this means these stars are visible anytime it is dark) and can be used as a landmark.  The best time to use the Big Dipper as a landmark is Winter mornings and Spring evenings.

  1. Look due north, the Big Dipper should be easy to see.  The Big Dipper is part of the constellation Ursa Major.  Locate the stars Dubhe (marked D on the chart), Merak (Me), Mizar (Mi), Alkaid (Al) and Muscida (Mu).  If you have reasonably good vision, you will see that Mizar is actually a double star.
  2. Follow Dubhe and Merak toward Polaris (marked P on the chart).  Nearby you will see two stars (both marked G), they are called the Guardians.  Polaris and the Guardians are the brightest stars of Ursa Minor.  If your skies are dark, you may be able to make out the other stars of Ursa Minor (which form the so called Little Dipper).
  3. Halfway between Mizar and the Guardians, you may see a dim star called Thuban (marked T).  Thuban is part of the constellation Draco; in dark skies you can trace the path of Draco which winds between Ursa Major and Ursa Minor until it ends at two stars (both marked Dr).
  4. Follow the arc formed by the stars Mizar (Mi) and Alkaid (Al) until you find the bright star Arcturus (A).  Arcturus is the brightest star of the constellation Boötes.
  5. If you see a bright “star” along the green curve that is not shown on this chart, it could be a planet.  Planets are not shown on this chart.
  6. You can continue the arc until you find another bright star Spica (labeled S).  Spica is the brightest star in the constellation Virgo (however Virgo can be a little difficult to make out in light polluted skies).
  7. Following Dubhe and Merak away from Polaris, you can find another bright star, Regulus (marked R on the chart).  Regulus is the brightest star in the constellation Leo.  Leo is easy to recognize even in light polluted skies.
  8. Between Leo and Ursa Major is a dim constellation called Leo Minor.
  9. Between Alkaid (Al) and Spica (S) is the star Cor Caroli (marked C on the chart).  Cor Caroli is the brightest star in Canes Venatici, Canes Venatici can be difficult to distinguish, there are only two bright stars in this constellation.
  10. Between Virgo and Canes Venatici is the constellation Coma Berenices.  It is somewhat dim and may be hard to locate in light polluted skies.
  11. In this diagram, Ursa Major is drawn suggesting Alkaid is the Bear’s nose.  However according to tradition Alkaid represents the tip of the Bear’s tail.  The lines were drawn this way to make the shape easier to find and remember.

Two dim constellations are not shown on this chart: Sextans (in the bottom right corner) and Camelopardalis (in the top right corner).

Summer Evenings & Spring Mornings

Summer Triangle

The Summer Triangle is visible in the Northern Hemisphere during Summer evenings and Spring mornings.  At these times the Summer Triangle can be used as a landmark; follow these directions.

  1. Find the Summer Triangle in the sky - there should be three bright stars overhead or high in the sky (note there are other “triangles” in the sky, if the following instructions don’t work, then you may have located the wrong group of three stars).
  2. The stars in the summer triangle are called Deneb (marked D on the chart) Altair (marked A on the chart) and Vega (marked V on the chart).
  3. Look closely near Deneb for the stars that make up Cygnus.  (Cygnus is also known as the Swan).
  4. Look near Vega for the stars that make up Lyra (also known as the Harp).
  5. Look near Altair for the stars that make up Aquila (also known as the Eagle), Delphinus (also known as the Dolphin) and Sagitta (also known as the Arrow).  Delphinus and Sagitta will be difficult to see if your skies are not dark (if so binoculars will help - Delphinus is a very attractive constellation in binoculars).
  6. From Lyra, locate a group of four stars that comprise the “head” of Hercules.  If your skies are dark and clear you may see the globular cluster M13 (marked GC on the chart).
  7. Using Hercules and Altair as a guide, locate the star Rasalhague (marked R on the chart).  Rasalhague is part of the constellation Ophiuchus (the Snake Holder).  Ophiuchus is near the constellation Serpens, Serpens has two parts: one part, Serpens Cauda (the Tail of the Snake) is shown on this chart.
  8. Using Hercules as a guide, locate the star Gemma (marked G on the chart).  Gemma is the brightest star in the constellation Corona Borealis (the Northern Crown).  While Gemma is reasonably bright, the remaining stars of Corona Borealis are not and will be difficult to see in light polluted skies.
  9. Now, if you look due south, you can see the constellations of Scorpius and Sagittarius (both are bright and easy to recognize, but not shown on this chart).  In dark skies you can see the Milky way starting at Sagittarius going across the sky through the Summer Triangle.

Not shown on this chart is Vulpecula (a very dim constellation near Sagitta).

Autumn Evenings and Summer Mornings

The Great Square

The Great Square is a group of four stars and is a good landmark to use in Autumn evenings and Summer mornings.

  1. Start by looking for the four bright stars that make up the Great Square.  They are marked S1, S2, S3 and A1.  S1, S2 and S3 are part of the constellation of Pegasus, and A1 (it has the name Alpheratz) is a star in the constellation Andromeda.
  2. If you follow along the backbone of Andromeda, you will locate stars marked A2 and A3 - note the gap between A1 and A2 is rather wide and there is moderately bright star in the middle.  Somewhat above the backbone is a fuzzy spot that will be visible in relatively dark skies, it is marked G on the chart and is the Andromeda Galaxy.
  3. Continuing along the backbone, you will reach P2 (called Algol).  P2 along with P1 (Algenib or Mirfak) make up the constellation of Perseus.
  4. Nearby look for a group of five stars in a “W” shape.  This is the constellation of Cassiopeia.
  5. In dark skies, you may notice the Milky Way passing through Cassiopeia.
  6. Next to Cassiopeia, look for the constellation of Cepheus.
  7. If you follow S1 and S3, they point to D (Denebe) which is part of the constellation of Cygnus.
  8. Between Cepheus and Pegasus is Lacerta (the Lizard).  It is a dim constellation which may be difficult to see.
  9. Near Andromeda is the constellation of Aries.  Aries has two relatively bright stars and several dimmer stars. The brightest of these stars, Hamal (Alpha Arietis), is marked H on the chart.
  10. Between Andromeda and Aries is the constellation of Triangulum.  Triangulum consists of three stars, two of which are brighter than the third. 
  11. If you see a bright “star” along the green curve, it could be a planet.  Planets are not shown on this chart.
  12. Pisces is a dim constellation that is difficult to make out.

Winter Evenings & Autumn Mornings

Orion

Orion is a bright, easy to recognize constellation visible in Autumn mornings and Winter evenings.  Use Orion as a landmark as follows:

  1. The star pattern of Orion is distinctive and made of bright stars.  You should note three stars in particular: Betelgeuse (B), Bellatrix (Be) and Rigel (R).  Halfway between the shoulder of Orion (Betelgeuse and Bellatrix) and his feet (Rigel) are the three belt stars.  You will note a set of stars that form a sword hanging from the belt; the middle star is not a star at all - it is the Orion Nebula (marked N on the chart), you may notice that appears blurry (look at it through binoculars).
  2. Orion is the part of the so called Winter Hexagon - to make out the hexagon start at Rigel and work clockwise.  You will find five other bright stars: Sirius (S), Procyon (P), Pollux (Po), Capella (C) and Aldebaran (A).
  3. Note, you may see bright “stars” along the green curved line, they may be planets.  Planets are not marked on this diagram.
  4. Sirius is part of Canis Major; try to make out the rest of Canis Major (dark skies are needed to see all of the stars).
  5. Procyon is part of Canis Minor.  There are only two bright stars in Canis Minor, Procyon and Gomeisa (G).
  6. Pollux is part of Gemini.  The outline of Gemini is relatively easy to recognize once you find Pollux (however some of the stars will not be visible in light polluted skies).
  7. Capella is part of the constellation Auriga.
  8. Aldebaran is the brightest star in Taurus.  Nearby you should see a compact group of six or more stars.  This is the Pleiades (marked Pl on the chart).
  9. Next to Auriga and Taurus, is Perseus.  You should find Algol (marked Al on the chart), then try to make out the rest of the constellation.  Algol is a variable star; if you carefully observe it over the course of few days, you might notice a change in brightness.
  10. Below Orion, you will be able to see the four brightest stars of Lepus (at least in dark skies), the rest of the constellation is harder to locate.

The following dim constellations are not marked on this chart: Monoceros (between Orion and Canis Minor), Eridanus (to the right of Orion), Aries (near Perseus) and Lynx (near Gemini).

References

For a list of the reference materials used to produce this guide, see the University Lowbrow Astronomer’s Book List.

Links

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