Finding your way amongst the Constellations
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The constellations are imaginary lines drawn between the stars to aid nagigation in the night sky. Some are named after ancient creatures, and others have been named more recently.
If you are completely unfamiliar with the sky then you should firstly attempt to find the brightest constellaions, and only later "star hop" to find the dimmer ones. If you are located in the northern hemisphere the Plough is a good choice. The Plough is only part of a larger constellation called Ursa Major ( the Great Bear). If you are above a latitude of about 42 degrees, then the Plough is "circumpolar" i.e. it never sets below the horizon.
The Spring Sky - Ursa Major
To find the plough you need to look north, and then either just to left or the right, above or below the point in the sky known as the celestial pole. This is due north, and equivilent in height in your sky to your latitude. e.g. If you are in London (latitude 51 degrees north) then, the pole will be 51 degrees high in the sky (just over half way to the zenith). The picture below shows the position of the plough in the sky relative to the north celestial pole (NCP) for the various seasons at 10 pm.
Below: The Plough is the tail of Ursa Major ( the Great Bear)
The main problem with identifing your first constellation is the scale difference between a map and the sky. Once you have spotted one constellation, the scale will be easier to work out for the rest.
Using the Plough as a celestial signpost in the sky is very useful. The different parts of it point to different constellations and bright stars very well. For example to find the bright star Arcturus in Böotes (the Herdsman), then you simply use the tail of the Plough to point the way (see below):
The other arrow on the diagram above shows how the two end stars of the bowl of the Plough point the way to the pole star (Polaris).
Another way that the Plough can be used as a celestial signpost is to point to Leo in the spring night sky. The two stars that point upwards to the pole star also point downwards to a point just above Regulus - the brightest star in Leo. You can continue to star hop to other constellations all the time - for example a line drawn between Regulus and the star that marks the hindquarters of Leo will lead you to the small constellation of Coma Berenices. This constellation contains a large star cluster which looks at its best through a pair of binoculars. (see below for diagram.)
The Winter Sky - Orion
From the northern hemisphere during winter Orion dominates the southern sky. In fact Orion is visable from all inhabited countries (in the southern hemisphere it is seen during summer in the northern regions of the sky). Orion (the Hunter) is pictured below. He carries a club in his right hand, and a skin in his left.
Orion is quite a large figure in the night sky. The key to finding him is his belt - the three stars of similar brightness running through the middle of the constellation. Just below this is Orion's sword. This is a verticle line of what appears to the naked eye as three stars, but in fact when viewed with a pair of binoculars or a telescope you will see that they are all double. This area is one of the most visited by amateur astronomers because it is home of the Orion nebula (M42). This is an emission nebula where new stars are born. It can be seen with the naked eye under a dark sky, and it can be seen well with binoculars, and details from within it can be seen at low powers with a telescope.
Orion is a good pointer to other constellations in the winter sky (summer if viewing from the southern hemisphere).
Above. The three belt stars point upwards to Aldebaren - the brightest star in the constellation Taurus (the Bull). Aldebaren is a red giant and its colour is very apparent even to the unaided eye. Aldebaren heads the v-shaped open cluster known as the hyades. This cluster is seen at its best through binoculars.
The three belt stars also point downwards to the brightest star in the sky - Sirius. Sirius is a white star with a white dwarf companion companion, but this requires a large telescope to see. Sirius means scorching in Greek, and the Egyptians used to use it to predict when the river Nile would flood. This was because the Nile always flooded soon after Sirius became visable in morning sky (the heliacal rising). Sirius is the primary star of the constellation Canis Major (the Great Dog).
The Summer Sky - Cygnus and the Summer Triangle
With the short hours of darkness during the summer months, there is not much time to stargaze when the sky is truely dark. Despite this the summer sky holds many delights for the amateur astronomer. The best place to start star-hopping in summer is the 'Summer Triangle' shown with dotted lines below. It connects the three brightest stars in the area: Deneb, Vega & Altair. I believe the Summer Triangle was a term first used by Patrick Moore on The Sky at Night.
Cygnus represents a swan in the heavens flying downwards with its head at the centre of the triangle.
The wings of Cygnus can be used to find the head of Draco, the celestial dragon.
Aquila, at the bottom apex of the Summer Triangle represents an Eagle. The general shape of this constellation can be used as a pointer
to the small, but very attractive celestial dolphin (Delphinus).
