Astronomy—A Beginner's Guide to the Night Sky
Credit to Nasa
Unless otherwise stated, photos on this page are credited to Nasa.
My thanks to Nasa - without these images, these webpages would not have been possible
N.B: Please note, all my articles are best read on desktops and laptops
This is the first of four pages presenting a beginner's guide to the night sky. And the clue really is in the title - there will be no complex astrophysics here. All these pages are intended as a basic pointer to objects which can be seen when you look up at the sky at night, not with a telescope, but with the naked eye or a decent pair of binoculars.
We look up at night and we see these points of light in the sky, so familiar to us, we all take them for granted and ignore them. Yet what we are seeing up there are the most astounding things that can be seen by any human being, and the statistics surrounding some of them are - quite literally - astronomical. My key purpose in writing these pages is to breathe a glimmer of interest into any enquiring minds - both young and old - in search of new discoveries. I hope for some, the pages might be the springboard to an interest which will fascinate for as long as one lives.
On this first page, there is no attempt to locate specific named objects to be viewed - that will be the aim of the three pages which follow. On this page my intention is simply to describe the types of objects up there, hopefully to enable an understanding of the differences between a point of light which is a planet, and a point of light which is a star, or a fuzzy cloud which is a comet or maybe a nebula or a possibly a galaxy.
Note: Visibility of objects in the night sky depends so much on one's own visual acuity, the obscuring glare of the Moon, the amount of dust in the atmosphere and - above all - street lighting. On a dark night in non-light polluted countryside, much much more can be seen with the naked eye than in the middle of a city. Therefore some of the objects listed on these pages which are visible to some viewers with naked eye vision, will be a challenge to others with binoculars. Please always bear this in mind.
These Four Pages
The four pages in this series are as follows:
- A Beginner's Guide to the Night Sky - the identification of the types of objects you can see in the sky at night.
- A Beginner's Guide to the Moon - what are the surface features on the Moon which we can see from Earth?
- A Beginner's Guide to the Stars - stars are not all the same. Some are like our Sun (which of course is a star), but others that we can see with the naked eye have a true vastness or a brightness which is almost unimaginable.
- A Beginner's Guide to Naked Eye and Binocular Objects in the Night Sky - other outstanding heavenly bodies to look out for in the sky at night.
Contents of Page One
- Light Years and Astronomical Distances
- Four Levels of Scale in the Night Sky
- Slow Moving Objects in the Night Sky
- Rapidly Moving Objects in the Night Sky
- Stationary Points of Light in the Night Sky
- Fuzzy Clouds and Smudges in the Night Sky
- How Do You Tell a Planet from a Srar?
- Why Doesn't the Night Sky Always Look the Same?
- The Zodiac
- Astronomy and Astrology
- Naked Eye Observing
- Binocular Observing
- Night Sky Maps
Photographs on this page for the most part are not intended to be spectacular or show great detail. Instead, they are intended to show night sky objects as they will appear to naked eye or binocular viewers.
Throughout these pages the term 'light year' will be frequently used. But what is a light year? It is a simple enough concept but frequently misunderstood - a light year is not a measure of time, it is a measure of distance. It is the distance light travels in one year, and as light travels at about 300,000 kilometres per second (186,000 miles every single second), a light year is an almost unimaginably great distance - about 10 million million kilometres (6 million million miles).
It is important to get some appreciation of these figures, because the scale of the various objects in the heavens may be hugely disproportionate to the way they appear to us - one point of light which superficially looks the same as another point of light may in reality be a million times bigger or a million times further away.
To put it into perspective, it only takes 1.5 seconds for light to travel from the Moon to the Earth, and 8 minutes for light to travel from the Sun to the Earth. yet it takes more than four years for light to travel from the very closest of the stars we see in the night sky, and more than 2 million years to travel from the furthest objects visible in binoculars!
Four Levels of Scale
Such is the scale of the Universe as briefly indicated above, that it may help to broadly categorise four levels of activity which we can see taking place in the night sky. Each level represents a huge increase in size and distance.
1) Atmospheric and Near-Atmospheric Phenomena : These include shooting stars and our own human enterprises such as aircraft, and nearby orbiting satellites, and all occur within 1000 km (600 miles) of the Earth's surface.
2) The Solar System : The Solar system of objects include all those which revolve around our Sun - planets, moons, asteroids and comets. Most lie within about 5 billion km (3 billion miles) or 4 'light hours' from Earth, though some comets may wander very much further away than this.
3) The Galaxy : The stars and nebulae lie way beyond the Solar System. Even the very nearest of these objects is more than 4 'light years' from Earth, and some visible stars are thousands of 'light years' distant. In other words, whereas it may take light a few minutes or a few hours to travel from the planets or from the Sun to the Earth, it takes decades, centuries or as long as human civilisation has existed, to travel from most of the stars. All the stars we see are just the nearest of more than 100 billion which all revolve within a colossal gravitationally bound mass called the Galaxy.
4) The Universe : Beyond our Galaxy there are many other galaxies and other objects which make up the entire Universe. The very nearest of these other galaxies (apart from a few relatively small ones) is not thousands, but millions of 'light years' distant, and yet it is visible to us through a pair of binoculars.
Now we will look at the objects which a beginner may see in the night sky, and how they may appear to the naked eye or to the user of binoculars.
Slow Moving Objects (Objects which Resemble Stars but which Visibly Move over the Course of a Few Minutes, in a Steady and Uniform Manner)
If you see a slow moving object steadily progressing across the night sky, it is not an astronomical body. It could conceivably be a very close by, man-made object such as a Chinese Lantern, or it may of course be an aeroplane (particularly if you can see flashing red and green lights!!) However, if the object resembles a star with a steady (not flashing) light, but moves uniformly in a straight line crossing the sky over a period of several minutes, it may well be a man-made satellite in orbit round the Earth.
Rapid Moving Objects (objects Resembling Stars Which Streak Across the Night Sky in a Few Seconds)
Any object which is seen streaking across the sky cannot be at great distance in outer space, though it may well be extraterrestrial in origin. The most likely culprit is a meteor or ‘shooting star’.
As well as planets and moons in orbit around the Sun, there are many smaller objects including asteroids and comets (described later). The smallest and most numerous of these are called meteoroids, and if a meteoroid happens to cross the orbit of the Earth and is captured by the Earth's gravity, then it will enter into our atmosphere at great speed. The friction generated causes the object - now called a meteor - to heat up to incandescence. The object literally bursts into fire, and at this stage becomes clearly visible against a dark sky as a shooting star (nothing of course to do with real stars). Meteors are usually very very small, perhaps only the size of a grain of sand, and consequently the streak of light produced may be very very brief, as the meteor burns itself out of existence in just a second or two. (On regular occasions throughout the year a 'meteor shower' may occur when shooting stars are very common in the night sky. These occur when the Earth passes through a particularly dusty region of space.
If the meteor is substantially bigger, then it will take longer to burn up and may be viewed as a glowing ball of fire streaking across the sky - literally, a fireball. And if the meteor creating the fireball is big enough, then a portion may survive passage through the atmosphere and strike the Earth leaving a lump of rock, now called a meteorite.
(Nothing else of extraterrestrial origin will be seen to be moving this fast - the only other lights which streak quickly across the night sky are produced by man-made objects such as rockets and low altitude jet aircraft).
Stationary Points of Light (Pinpoint Objects Which Do Not Move over the Course of a Few Minutes of Viewing)
Stars - Almost all of those pinpricks of light in the night sky are, of course, stars - vast balls of super hot burning gas just like our Sun. The reason why they appear so small is because they are at incredibly huge distances from us - at least 100,000 times more distant than our own star, the Sun.
Planets - Of all the pinpricks of light you can see with the naked eye, just five may be something different. They are planets - far far smaller than stars and much much closer to us - some are closer to us than the Sun, and some are further away, but compared to all the stars, they really are our next door neighbours. Earth is a planet, and the other planets are similar balls of rock, or alternatively cold globes of gas, which orbit our star, the Sun, Unlike the stars, they do not generate their own light, and can only be seen because they are reflecting the light of the Sun. The five which we can see with the naked eye are Mercury, Venus, Mars, Jupiter and Saturn.
Moons - Moons are natural satellites of planets - small rocky bodies which also go around the Sun, but their primary orbit of revolution is around their host planet. Only one moon - our own - is visible to the naked eye. Four others are visible in binoculars. These are four of the moons of Jupiter.
Asteroids - The asteroids are rocky objects, usually much smaller than moons, which mostly orbit the Sun between Mars and Jupiter, though some stray further away or closer, and may even cross the orbit of the Earth. Only one - Vesta - is theoretically visible to the naked eye, though you need to know exactly where to look, and a very clear sky to see it.
(Very rarely an asteroid may stray so close to the Earth that it becomes clearly visible. Much much more rarely, it may be pulled in by the Earth's gravity - the stuff of fictional nightmares like 'Deep Impact' and 'Armageddon' and the real-life asteroid which caused the extinction of the dinosaurs!)
Supernovae - I'll mention supernovae, but for the purpose of this series of articles, we will then immediately forget them. Supernovae are particularly massive, unstable stars which literally explode, giving off vast amounts of heat and light. If this happens, a star which has previously been too dim to even see with the naked eye, may suddenly become visible even in daylight. However, such events which are close enough to be observed without good equipment, take place less often than once per 100 years, and indeed only seven are known to have been seen before the invention of the telescope in the 17th century. If one happens in our lifetimes, it'll be all over the news broadcasts, so you'll know about it!
There is a less destructive, but still violent explosive stellar event which is simply called a nova. These are more frequent than supernovae, but because they do not involve quite such an intense brightening of the star, they are still rarely visible to the naked eye here on Earth.
That's all the types of stationary pinpricks of light to be seen in the night sky (though note the mention of comets below). To all intents and purposes, we can forget about supernovae, novae and asteroids, so all stationary pinpricks of light you see will be stars (about 99%), planets (maximum of five, but probably no more than two or three at any given moment) and moons (just our own Moon which isn't a pinprick, or four more if you look at Jupiter through binoculars).
Fuzzy Clouds and Smudges
If you see a faint, cloudy patch in the dark night sky, of course it may be just that - a wispy bit of cloud. But if it stays in the same place relative to the stars for a few minutes, or an hour, or if it’s still there 24 hours later, then you know you’ve got something special. A fuzzy cloud in outer space may be a comet in our Solar System, but the chances are it’s something all together more exotic - millions of times farther away, and a billion times more intrinsically brilliant. Basically there are just five types of astronomical object which can be seen as a fuzzy patch of light in the sky - the aforementioned comets, open star clusters, globular star clusters, nebulae and galaxies.
Comets - Comets are mixtures of rock and ice, often described as being like dirty snowballs. They orbit the Sun just as planets and asteroids do, but with far more eccentric orbits which may take them very close to the Sun (or Earth), but also many thousands of times further away, beyond the orbit of any planet. On occasion when a comet comes close to the Sun it may become visible to the naked eye, possibly as a point of light, but usually as a fuzzy smudge of light. Sometimes the comet may become elongated with a very long tail-like structure, although these are rarely spectacular. The tail is caused by solar radiation causing gas and dust particles to stream out away from the head or nucleus of the comet. There have been no really brilliant comets with tails extending across the sky in living memory, though there's been several visible to the naked eye. A brief mention will also be made on Page 4.
Open Star Clusters - There are some cloudy smudges in the sky which are really quite distinct. One such is the Pleiades or 'Seven Sisters' in the northern hemisphere - probably the most prominent of all. Looking at such objects through a pair of binoculars or a telescope will resolve the cloud into numerous points of light - stars. These objects are called open star clusters, and they are groups of stars which are genuinely quite close together in space. The reason they are close together is because all the stars within the cluster have formed out of the same primordial dust and gas cloud in the relatively recent past, and they haven't yet had time to move far apart. Most open star clusters cover an area of space a few light years in diameter.
Globular Star Clusters - In open star clusters there may be several dozen stars or even a few hundred, but there is another object which is far grander in scale - the globular star cluster. These are exactly as the name suggests; they are great balls of stars, often containing many tens of thousands or even millions of stars, tightly held together by gravity over an area of more than a hundred light years in diameter. They are quite different in origin to open clusters, and by contrast they are mostly composed of very old stars, and all are many thousands of light years distant. This great distance means that the individual stars cannot be made out, and indeed few of the clusters are even visible to the naked eye. But some - including the Great Hercules Cluster in the northern hemisphere - can be viewed as a smudge of light in binoculars, and a related object - Omega Centauri - should be naked eye visible in the southern hemisphere.
Nebulae - Nebulae are great clouds of gas and dust in outer space, most of which are many thousands of light years distant, and several light years in diameter. Some are dark, and stop all light from shining through them, but others are the site of new star formation and these are visible either by emission or reflection of starlight. Only a few are clearly visible to the naked eye, but some others are visible with binoculars. The best known and easiest to find is the Orion Nebula.
Galaxies - As we've already said, if you can find a hazy patch of light in the sky which remains permanently in one place, the chances are that you are looking at something very big, and very very distant. With binoculars, some of these fuzzy patches of light may be resolved into many pinpricks of light, (open star clusters) while others will just remain as fuzzy patches (globular clusters and nebulae). However, some are even more special than this. All the objects so far mentioned are to be found within our own galaxy. But it is possible at night to see another galaxy, entirely separate from our own, and not merely 'light minutes' or 'light hours' distant (like the Sun, planets, asteroids and comets), or even tens, hundreds or thousands of light years away (like the stars, star clusters and nebulae). Galaxies are vast accumulations of billions of stars revolving around a massive central nucleus, and they are many millions of light years distant. There are two or three visible to the naked eye and binocular vision.
The Milky Way - If you live in a fairly light pollution-free region then you may be fortunate enough to see the Milky Way, named for the soft white colour of this band across the sky. For a long time the nature of this was the subject of speculation, but now it is known that the Milky Way is our view of the myriad of stars in the direction of the distant centre of our own Galaxy. It will be discussed and explained on Page 4 of these guides.
How Do You Tell a Planet from a Star?
Fuzzy patches of light may represent the most remarkable of space objects, but it is those pinpricks of light - the stars and planets - which are most apparent to the casual viewer. There are, I repeat, just five planets which are quite clearly visible with the naked eye. It follows that almost all points of light in the night sky are stars. But how do you know for sure you are looking at a star, and not a planet?
There are actually several ways. Firstly, if you can identify the star Sirius (for its location, see Page 3, 'A Beginner's Guide to the Stars'), then you will have a benchmark of stellar brightness, because this is the brightest star we can see with the naked eye. It follows that if we see a brighter point of light, it cannot be a star - it is a planet. Specifically two planets - Venus and Jupiter - are frequently MUCH brighter than Sirius or any other star.
Secondly, if you see a bright light close to the setting or rising Sun, it may be a star, but it is more likely to be Venus or Mercury, both of which are often bright, and both of which never stray far from the Sun (because their orbits are closer to the Sun than ours).
Thirdly, there is 'twinkling star syndrome'. Why do stars twinkle? It is because they are utterly brilliant but tiny points of light (to our eyes), billions and billions of kilometres distant. They have no effective diameter in the night sky (even in a large telescope), so even small particles of dust in our atmosphere can cause the starlight to momentarily dim or 'twinkle'. Planets are much closer, and a small telescope will reveal a disc of measurable diameter. It takes much more dust to obscure a planet's reflected light and cause it to twinkle, so the light from planets may appear more uniform. Please be aware though, this is not a totally reliable method of telling planets from stars! So much will depend on the amount of dust the light is passing through, and the current distance of the particular planet you are looking at, and hence its apparent diameter (planets can vary in their distance from the Earth by a huge amount depending on where they are in their orbit around the Sun).
The best method to distinguish stars from planets is to get hold of a star map and simply become aware of the patterns of stars in the sky. Although stars appear to move around the sky during the course of a night or a year (it's really the rotation and tilting of the Earth on its axis, which makes them appear to move), the stars keep their positions relative to each other. For example, the Plough' or 'Big dipper' will always have this shape during our lifetimes - none of the seven stars in the picture below will move away from the others. Stars never leave the constellation they appear in. Planets are different. Planets wander through different stellar constellations. One month Saturn might be in the constellation of Aquarius, another month it might be in the constellation of Taurus. So if you have a star map and you see a bright point of light in the sky which isn't marked on the map, then it will almost certainly be a planet. (More about this in the 'Beginner's Guide to Naked Eye and Binocular Objects Page).
Why Doesn't the Night Sky Always Look the Same?
We've already seen that some objects move against the backdrop of stars - comets, asteroids and planets for example - but what about the stars themselves? Although the constellations may look the same shape from one year to the next, their location in the sky changes drastically throughout the course of a night, and throughout the year. Why? The simple answer to this question is that the Earth is in constant motion. Not only are we orbiting around the Sun, but we are also spinning on our north-south axis, and we are 'wobbling' - tilting first one hemisphere, then the other towards the Sun.
- The spin or rotation of the Earth on its north-south axis gives us our day length, but of course there is another, visual effect - as our planet rotates, so the stars appear to change their position relative to us, and rotate around the night sky.
- The tilt of the Earth gives us our seasons depending upon whether our own position on the planet is directly facing the Sun, or is tilted more obliquely to it. But of course if it changes the apparent position of the Sun in the daytime sky, it follows that it will also change the apparent position of the stars in the night sky, and for this reason some stars and constellations are only visible at certain times of the year.
It is beyond the scope of this page to go into the precise methods in which the night sky changes, on a daily or seasonal basis, but some details will be given in relation to specific stars such as Polaris and Sirius on Page 3 of this series.
Suffice it to say here, that on a nightly, monthly or yearly basis, all the observed changes in the position of stars and other far distant objects (as opposed to Solar System bodies like planets, comets and asteroids), are simply down to movements of the Earth made apparent in the changing portion of the night sky we can see at any given time or given latitude. Do the stars themselves actually move? Well yes, they do, and very fast too as they all - including our Sun - orbit the centre of our Galaxy. Indeed given enough time, even the constellations themselves will change shape as some stars move away at faster rates than others. But the distances to all the stars are colossal, and just as a plane appears to be moving slower and slower the further away it is from us, so these stellar movements cannot be detected by the naked eye, even over the course of a lifetime. Go back to prehistoric times however, and some of the constellations we now see would have looked very different as a result of this very real stellar movement.
The Zodiac is a region of space which is marked out by 12 of the ancient Greek constellations. In real terms what the Zodiac actually marks out is the plane of space or 'Ecliptic' through which the Earth's orbit around the Sun lies, and the 12 constellations which happen to lie in that same plane. The significance for the Greeks was that due to the fact that the other planets in the Solar System also lie in (roughly) the same plane as the Earth and Sun, these are the 12 constellations through which all the planets appear to pass (of course in reality this is merely a line of sight phenomenon - the stars in the constellation are very much further away than the planets).
The Earth's ecliptic plane lies more or less in line with the equator (varying by 23° between the Tropics of Cancer and Capricorn). In these tropical regions, when the Sun is directly overhead in the daytime, the Zodiacal constellation on the opposite side of the Earth will be directly overhead at night. But the Zodiacal constellation 'through which the Sun is passing' will be invisible, because it will be in the same direction as the Sun during the day time. It is this constellation for which the time of year is named.
For example during much of December, the Sun is in front of Sagittarius, so in Astrological terms this period is known as Sagittarius, even though that constellation will not be visible in the night sky.
We've mentioned constellations a few times already, but now we must talk about these in a little more detail.
Constellations are merely patterns of stars in the sky. Occasionally there may be a physical link between some of the stars in a constellation, but for the most part constellations have no astronomical significance whatsoever. Indeed one star in a constellation may be many hundreds of times further away from us than another; they only look like they are close together as they happen to be in almost the same line of sight. Traditional constellations were named by the ancient Greeks, but since then, exploration of the Southern Hemisphere has led to numerous new constellations being created.
For the required accuracy of modern astronomy, scientists now divide up the sky into sectors with two co-ordinates which are called Right Ascension (R.A) and Declination (DEC). These are a bit similar to latitude and longitude on Earth, and just as latitude and longitude can precisely define the position of any place on Earth, so R.A and DEC can give the precise location of any object in the night sky. However, it is very difficult for a beginner to access this kind of information and relate it to a point in space. Basically it's much easier visually to recognise patterns of stars in the sky and to say for example that the star Rigel, as viewed from the northern hemisphere, is the bottom right star of the Constellation of Orion, even though it is more accurate to say it is at '05hrs 14 mins R.A and -08° 12 mins DEC'. (For the purposes of these pages we shall therefore forget R.A and DEC and give positions in relation to the constellations where heavenly bodies are to be found).
Astronomy and Astrology
Mention of constellations brings us - unfortunately - to the subject of astrology. I'm almost loathe to mention astrology, but millions of people know their 'star sign', and the constellation it represents, and will they read their horoscopes eagerly and regularly. Astrology is the belief we can understand something of one's character and personality and predict their future, by the 'sign' under which they were born. Astronomy is the scientific study of objects and phenomena in space, based upon observation, analysis, experimentation and exploration, and the application of known physics, chemistry and mathematical equations. Many people still confuse the two, but let us be clear:
People can believe in astrology if they wish, but astrology has no proven basis in fact, and no credible methodology. It is not a science. To call an 'astronomer' an 'astrologer' is just about the greatest insult one can bestow upon an analytical, objective scientist. DON'T DO IT! They may hit you :)
Naked Eye Exploring
A pair of eyes is the only optical instrument you need to start observing the stars, and definitely the best way to start finding your way around the night sky. And there are quite a few advantages to just using the naked eye:
1) An overall perspective. You can see the star patterns of the more distinctive constellations like Ursa Major or Orion, and you can see how adjacent constellations relate to each other - something you cannot see in the much smaller field of view of a pair of binoculars, much less a telescope, in which only a tiny part of a constellation will be visible. You can also see exactly how constellations appear and disappear at the horizon, or rotate around the sky at night.
2) Making Comparisons. You can instantly compare the brightnesses of objects in different parts of the sky with just a glance to the left or right, or by raising or lowering your sights, and this will certainly help you identify these objects - you can't do this with either binoculars or telescopes.
3) Relating what you see in the night sky to what you see on a star map. As soon as you look through binoculars or telescopes, you will see a myriad of stars, and it is much more difficult to relate this to what you see on a star map where only the brightest stars are shown. With the naked eye, it will be much easier to identify the brighter objects in the sky with those on the map.
4) Shooting stars. You can see those brief fleeting objects like shooting stars with the naked eye. You cannot really hope to catch these in binoculars or a telescope.
Beyond naked eye star gazing, binoculars are undoubtedly the next step. You don't need a telescope for most of the observations I am covering, and again there are several advantages to using binoculars:
1) The Moon. Binoculars allow much greater detail to be seen on the Moon than is possible with the naked eye.
2) Identifying planets. Binoculars can sometimes resolve a planet into a disc of clear diameter, whereas stars will always remain points of light.
3) Observing faint objects. Of course with the best will in the world, many of the dimmer stars and the most interesting objects in the night sky such as faint nebulae and star clusters and the moons of Jupiter, cannot be seen with the naked eye, but can be clearly seen with binoculars.
4) Allowing clearer, easier viewing than a telescope. The magnifications involved in telescope observing are just too great to locate fainter objects without sophisticated tracking equipment, This is because you can only see a tiny portion of the sky at a time. Unless you know exactly where to look in the sky, you will find it very hard initially to locate anything with a telescope.
What to Look for When Buying Binoculars
When purchasing a pair of binoculars the thing to look for are two numbers in the specification. Usually they will be expressed rather like 7 X 35, or 10 X 50. But these are not multiplication sums - the two numbers express quite different properties of the binoculars.
The first, smaller number is the magnification. For astronomical purposes you want a pair of binoculars with at least 7 times magnification. But if you go much beyond 10 times, the binoculars will not only be increasingly heavy, but any hand shake will be magnified, and a tripod may be needed to keep the image steady.
The second figure refers to the aperture or diameter of the lens in millimetres. The importance of this figure is that a larger aperture lets in more light, and the more light you allow in from an astronomical body, the more clearly you will be able to see it. Allow at least 40 mm for a good lens aperture.
An excellent little article on the mechanics of binoculars and the uses to which they can be put, is to be found at the Astronomy Magazine website. In these four pages most of the heavenly bodies descibed will be naked-eye visible, but where binoculars are particularly useful, this will be mentioned in the text.
Night Sky Maps
Finally on this page, I must recommend that you buy or download a star map. There is no value in displaying a map on this page, because it would only be accurate at one specific place, date and time. The latitude of the observer, the seasonal tilting of the Earth and the nightly rotation of the Earth, all change the aspect of the sky which can be seen at any location, month of the year, or time of night. However a star map will be essential to find your way around the heavens. There are two options here.
First you can use a star map programme on the Internet. The advantage of this is that you can change the co-ordinates on the map to suit your location and viewing time. You can also add more information to the map or alternatively de-clutter the map by personalising the range of objects shown. Finally an Internet map will constantly update to show new objects such as an approaching comet or asteroid: Options include:
- you can choose to show only naked eye stars, or binocular visible objects.
- You can include or exclude the names of stars or constellations.
- You can include or exclude objects such as planets, comets, nebulae and galaxies.
The second alternative is to print up a map, or better still buy a star map or book of maps. The advantage of this is that you have something you can hold outside whilst watching the skies (particularly useful as you usually have to hold the map above your head to effectively reproduce the sky you are looking at). You can also easily rotate the map according to whether you are looking due south, or east, or north, or whatever.
Whichever type of map you use, and however good it is, it is still, I must admit, rather difficult to get your bearings at first - partly because you are looking at a hemispherical dome of sky and trying to relate it to a flat, two dimensional map. But it should not take long to identify the most conspicuous and unmistakable constellations and soon you will be able to find these without the aid of a map. And if you look often at the night sky, you will gradually appreciate how the stars seem to rotate around the heavens during the night and how some appear or disappear at the horizon during the year. It will not be too long before you require the map only to locate the less predictable objects in the night sky such as the wandering planets, and the occasional comets or asteroids.
Decent free sky maps can be downloaded at the following locations, but if you have a real interest, then a bought map, or specialist CD ROM programme is advisable.
The Sky (by John Walker)
Sky Maps (by Skymaps.com)
All Sky U.K Star Chart (by Astronomy Now)
This first Beginner’s Guide to the Night Sky has sought to identify the various kinds of objects which one can see with the naked eye or binoculars, and how to quickly tell them apart. It has also attempted to give a very brief idea of the distances and scale of these objects. Finally the page has given a little general information on other aspects of night sky observing, such as star maps, what to look for when buying binoculars, and changes which occur over time in the night sky.
The page however has not indicated much in the way of specific named objects we should be looking for and the details of these. That is the subject of the next three pages which will concentrate on our Moon, the stars, and all other objects, repectively.
Hopefully you’ll stay with me as we go on this journey to see what we can see out there in the night sky. And believe me, what we can see with our eyes - and also with our imaginations - is pretty spectacular …
Questions & Answers
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