First Light Guides: The Basics

It helps to know a few basic patterns, and how to know if you are seeing them.  For example, many people think that the Pleiades is the Little Dipper, but a simple hand measurement will quickly show that it is not.  Others have a hard time finding Orion, not realizing that depending your location, it can look much, much larger than how it appears on a star chart!  And, once these few basic patterns are known, it is much easier to find other constellations by either using them to point to other stars/patterns, or looking between these well-known ones.

IMPORTANT: If you are unable to see/locate the slightly dimmer, 2nd magnitude stars in the Big Dipper, Cassiopeia or Pegasus, it may be difficult for you to locate many of the objects in the guides located here.

When you are ready to get started, click here to see the charts to compare to your sky tonight.

The Northern Night Sky

Let's start in the northern sky.  To begin, remember that the north celestial pole - which is very near the star Polaris - is the same number of degrees above the horizon as your latitude.  These charts show a 40 degrees north latitude.  For lower latitudes, Polaris - and the constellations shown in the north - will be lower.  For higher latitudes, they will be higher in the northern sky.  Let's start with one of the most recognizable patterns:

The Big Dipper (or Plough, as it is called in the U.K.).  Now, the Big Dipper is an asterism - or a pattern of stars - that looks like a given object.  The larger Ursa Major (Big Bear) constellation extends beyond the Big Dipper, so we just want to concentrate on the 7 Dipper stars, which are the brighter ones of the constellation anyway.  The rest of Ursa Major is dimmer, and harder to see from many urban locations, but the Dipper can usually be seen, being composed of largely 2nd magnitude stars.

Look at the chart below.  This shows how the sky looks, approximately, in early spring facing north.  There are five star locations labelled.  It is not important to know the star names just yet.  Simply note that the distance from star 1 to star 2, is about 25 degrees.  The distance between stars 2 and 3 (star 3 is Polaris, incidentally) is nearly 30 degrees - slightly farther than the first two.  Use the measuring techniques from the Stargazing Basics series to determine if you are seeing them.  On the western side of this view is a "W" shaped set of stars.   This is Cassiopeia.  The distance from stars 4 and 5 is only 13 degrees, slightly less than across your fist held at arm's length. 

View of northern sky

As the sky rotates due to the rotation of Earth, as well as it's revolution, where these stars are may be different.  For example, in early autumn in the evening, you may see them look more like the graphic below.  Note how the two constellations have reversed locations compared to Polaris (star 3).  The "W" is now lying on it's other side, and the seven "dipper" stars of Ursa Major now are with the "bowl" down and the "handle" up.

Because this page does not detail how the stars change with the seasons, click to see this (offsite) page, which may be helpful to understanding that.

Of note, these stars may also be seen in other locations around Polaris.  For example, the Big Dipper may be seen well up in the sky, near overhead.  When this occurs, Cassiopeia will be either just above or slightly below the horizon.  Similarly, when Cassiopeia is very high in the sky overhead, the Big Dipper will be low to the horizon as well.  These two shaps are nearly opposite each other from Polaris in the sky, and hence rotate around that star from each other.

The northern sky, autumn

The Overhead Night Sky

From there, we can begin to look for constellations and patterns that are seen more overhead in the sky.  Some of these may pass the zenith, depending on your latitude.  If you are more south, some may appear north of the zenith; if you live in northern latitudes, some of these may appear further south than your zenith.  

In winter, there are more bright stars towards the south and overhead.  In summer, though we are generally looking more towards the center of our Milky Way galaxy, there are fewer bright stars.  However, three prominent ones help guide us in those months.  High overhead in early/mid-summer evenings is the Summer Triangle of stars, which is not a constellation, but rather a convenient asterism of three bright suns.  The brightest, Vega, is in the constellation Lyra.  The next brightest, and furthest south, is Altair in Aquila.  The dimmest, but still a first magnitude stars, is Deneb in Cygnus.  Here are the distances between each, so you can measure these and determine for certain if you are seeing the Summer Triangle (all distances approximate with a 5 degree tolerance):

  • Vega to Deneb: 25 degrees
  • Vega to Altair: 35 degrees (use two hands to measure this)
  • Altair to Deneb: 40 degrees (use two hands to measure this)

Check out this chart below, and compare what you see in the sky overhead during summer evenings:

The Summer Triangle

Moving on to the autumn evening sky, we find a slightly dimmer set of stars, but ones that are in a nearly square-like shape - and, nearly identical in brightness.  These stars are all nearly 15 degrees apart from each other, which makes it a snap to identify them.  They belong to the "wings" of the flying horse Pegasus, though technically one is part of the chained Princess Andromeda.  But no matter; what is important for our purposes is knowing how to measure and identify them.  These are usually found in the evening, autumn sky, and from 40 to 50 degrees latitude, nearly overhead as well.  Note that their brightness will be similar to the Cassiopeia and Big Dipper stars, and dimmer than the Summer Triangle stars (which are often still visible to the west of the "Square").

The Great Square of Pegasus

Moving on to winter skies, though there are brighter stars overhead, the most distinctive pattern is now found in the southern sky.  Three, 2nd magnitude stars, nearly equidistant and almost in a straight line, form a "belt" for Orion the Hunter, and these stars are surrounded by two more 2-nd magnitude stars and two 1st magnitude stars.  Even if you have seen Orion and not known what it is, you have undoubtedly seen these stars at some time.  The are nearly due south in the evenings of early winter, but in early winter / late autumn, they may be slightly tilted and rising in the southeast.  By late winter, they are often tilted the other way, and setting in the southwest.  But any way you look at them, the stars of Orion are easy to see and identify.  However, they do appear farther apart than how they may look on a screen or star chart, so here are some handy identifying measurements:

  • Across the "belt" stars: 3 degrees
  • Left belt star to upper left "shoulder" star (Betelgeuse):10 degrees
  • Upper right star to lower left star: 15 degrees
  • Upper left star (orange looking Betelgeuse) to lower right (blue looking Rigel): 20 degrees

Take a look at the chart below and see if you can identify Orion in your winter sky:

Orion in the winter sky

Those are the very basic star patterns you will need to know to use these object locater guides, and it is likely that you are familiar with some - of not all - of them. If you would like more information on how to find and identify more constellations and bright stars in the night sky, see the following pages here at Eyes on the Sky:

Ready to get started?  Click here to see the charts to compare to your sky tonight.