We are familiar with occultations of the Sun and the Moon. We give these occultations a special name – eclipses – solar eclipse for the Sun and lunar eclipse for the Moon.

Lunar Eclipses

A lunar eclipse occurs when the Earth, Sun and Moon are aligned, with the Earth between the Sun and the Moon.

The Earth is three times larger in diameter than the Moon, so it easily blocks out the Sun’s light and casts a shadow on the Moon.

The Moon of course, does not produce light itself, only reflecting sunlight, so it looks dark during an eclipse.

In fact the degree of darkness does vary due to the condition of Earth’s atmosphere. If Earth’s atmosphere is clean, it will bend sunlight to some extent and this gives the Moon a slight illumination.

If however Earth’s atmosphere is dusty, as happens after major volcanic eruptions, it does not bend sunlight so much and a lunar eclipse can be a very dark one.

As the Moon orbits around the Earth once every month approximately, you might expect there to be a lunar eclipse each month, but this does not happen.

The reason is that the orbit of the Moon is inclined a few degrees to the orbit of the Earth. This ensures the Moon does not pass into the Earth’s shadow every month.

However, lunar eclipses are more often seen than solar eclipses because when they do occur, they can be seen from everywhere on Earth where the Moon can be seen at that time.

When a solar eclipses takes place, it can only be seen from a narrow strip of places on Earth. The path of totality tracks across the Earth’s surface, with a strip of partial totality on either side.

Solar Eclipses

WARNING… Never, ever look at the Sun through binoculars or a telescope, as you will certainly damage your sight. Observe an eclipse only by projecting the Sun’s image onto a sheet of card.

Solar eclipses happen when the Moon is aligned between the Sun and Earth, so that sunlight is blocked-out and a shadow is cast on the Earth.

This gives a remarkable effect here on Earth, as the Sun is obscured and then reappears some minutes later.

From a particular point on Earth, a solar eclipse is sometimes partial, and occasionally total, meaning that the Sun is completely covered by the Moon.

During a total eclipse, the Moon just about exactly covers the Sun. This is remarkable in itself.

The Moon covers the Sun in this way because the ratio of their diameters, happens to be very similar to the ratio of their distances from the Earth.

Putting it another way, the Sun and Moon have roughly the same angular size in the Earth’s sky.

This exact coverage gives rise to wonderful effects at the edge of the Sun during total eclipses such as the “diamond ring” and the “string of beads”.

It has also enabled astronomers to study phenomena very close to the Sun’s surface, such as solar prominences and the Sun’s corona.

Other Occultations

Occultations of other objects in the sky are always keenly observed and have been important to astronomers in the past.

Lunar occultations are when the Moon passes in front of a star or planet and this is interesting to observe. The Moon has no atmosphere, so stars suddenly disappear without any fading and then later, suddenly come back.

Double stars have been discovered through observing lunar occultations.

Sometimes, an star will “graze” the edge of the Moon, revealing details of hills and mountains on the Moon, as the star disappears and then reappears several times.

As recently as 1977, faint rings were discovered around the planet Uranus because a star flickered as it was occulted by Uranus.

Most people will have heard the term “constellation” and will know that it relates to patterns of stars in the sky.

Many people will probably think of astrology and the “Signs of the Zodiac”, for example Aquarius and Pisces.

But how many people know what the constellations actually are?

The star constellations are really just a fairly arbitrary way of dividing up the night sky, in a memorable way.

But arbitrary or not, the constellations are very useful and help observers to find their way around.

Dividing the sky up in this way, probably started as long ago as humankind itself.

Early people certainly drew recognisable shapes representing star patterns and also began to associate these shapes, with Gods or important legends and stories.

The constellations became somewhat more precisely defined with the early Greek astronomers, who classified a total of 48 star patterns.

At this time, the notion of the “Zodiac” stars also began. The Zodiac is the 12 star patterns or constellations, that the Sun appears to pass through, during the 12 months of the Earth year.

Hence the idea of each constellation being associated with a specific month of the year.

Interestingly, there should probably be thirteen signs in the Zodiac, because the Sun does actually pass through the constellation of Ophiuchus, as it is now defined!

There is one very important point to make about the constellations. Each constellation is not a real grouping of stars – it is only the appearance of a group, from our viewpoint here on Earth.

In fact, the stars in any particular constellation are at greatly different distances from Earth. So if we were to see them from a different position in our galaxy, they would not look like a group at all.

The constellations as astronomers know them today, were defined properly in the 1930′s, by the International Astronomical Union (IAU).

There are now 88 constellations. They vary in size, but generally, each constellation extends beyond the recognisable pattern of naked-eye stars (called an asterism) into the surrounding sky.

So for example, the constellation of Ursa Major contains the highly recognisable shape of the “Plough” or the “Big Dipper”. This is called an asterism.

The Plough asterism is made up of seven stars that appear bright to us on Earth. But the constellation of Ursa Major is much larger and contains many, many more stars and indeed other galaxies, that we can observe.

Taken together, the 88 constellations map out the entire sky into 88 areas. This is very useful to astronomers, when they want to describe where an object may be observed.

This is about 2.5 million light years away and is visible during autumn and winter as a hazy patch in Andromeda. It’s easy to see from country skies.

Some people with very good skies or very good eyesight, or both, can see an even more distant galaxy called M33, in the nearby constellation of Triangulum.

Generally, this is a very good thing. You can now buy a very capable, powerful instrument for a remarkable price.

It is not unusual for amateurs to obtain a 6 inch, 8 inch, or even 10 inch aperture telescope, quite possibly as their first serious instrument for astronomy. And, built-in computerised control is becoming common.

As I say, this is good.

However, I think a few words on the real-world practicalities of using these telescopes, may be helpful to beginners, before they part with their money.

I am certainly not trying to put you off buying a decent sized telescope. I encourage you to do so, assuming you are interested in astronomy and can afford it.

Just think through these practical aspects in advance and it will be all the more enjoyable.

Storing The Telescope

Telescopes are large items and they have an awkward shape. They take up quite a lot of space in a small house, even if they can be partly dismantled, say by removing the tripod.

They need to be protected when not in use, from dust, moisture, excessive heat and cold, being knocked over and inquisitive children who want to take them to pieces.

Consequently, you need a large cupboard or a corner of a special room, that can be set aside to store your telescope.

Assembling The Telescope And Moving It Outside

Telescopes are heavy, particularly if they are larger than 6 inch aperture.

Also, you may have to do some limited reassembly, like putting it back onto the tripod, before it is ready for use.

At 8 inch aperture and above, moving the telescope safely is really a two-person job. Think about this before you spend thousands on a large telescope

Firm Mounting

To get good results, you need a flat, solid area to site the telescope. When you use even moderate magnification, any movement in the floor surface will drive you mad, as you try to track faint objects.

A wobbly wooden deck is not much good.

Concrete is firm, but if it has been heated by the Sun, it generates thermal air currents moving upwards past the telescope. This spoils the image.

Grass, providing it is dry and firm, is surprisingly good as a base for your telescope, as thermal effects are limited.

Cooling Down Time

A refractor or schmidt cassegrain telescope is sealed and so it does not need very long to aclimatise to the outside temperature.

A reflector is very different, however.

Don’t think you can take one out of a warm room and put it outside where the temperature is 20 degrees lower, and then immediately see good images.

A reflector takes up to two hours to settle to thermal equilibrium with the outside temperature. Only then will it provide good images.

As any telescope cools, dew starts to form on the lenses and mirrors. This is frustrating. A dew shield can help, but some people experiment with mild electrical heating to dispel the moisture.

Aligning The Telescope

“Go-To” computer controlled telescopes are very tempting, especially for beginners who do not know their way about the night sky and generally, they are very good.

This type of telescope is common now. It has a computer that will automatically point the telescope at the celestial object you want to observe. Telescope dealers use this as a BIG selling point.

However, the Go To system will find nothing unless the telescope has been accurately aligned.

This involves entering certain settings for latitude, date and local time into the computer and then going through an alignment process, usually involving the finding of two bright stars.

In my experience, many people find this alignment process difficult and time-consuming.

It can totally spoil the idea of “just popping outside with the telescope” to observe something.

So please bear in mind, that Go-To controllers need proper setting up, if they are to work as promised.

If you find it difficult to use a computer, say to find and use websites on the internet, you will find it tricky to use a computerised telescope Go-To system properly.

Summary

None of these points are meant in any way to put you off buying a good telescope. Modern commercially produced telescopes offer fantastic value for money, compared to what used to be available.

I suggest only that you give these practical considerations some thought before you purchase. Then your new telescope should give you the rewarding experience, it is surely capable of delivering.

Just go onto the internet and do a search for “astronomy society”, together with your location. Most societies have a website, so you should find out if there is one local to you.

If you don’t find a society that suits your needs that way, then in the UK at least, the website of the Federation Of Astronomical Societies is a good place to look.

Don’t feel intimidated by your relative lack of astronomical knowledge or imagine that you will look stupid. In my experience, it is just not like that.

Most societies are always looking for new members and will welcome you, whatever your level of knowledge or experience.

And often, enthusiasm is better than knowledge and experience, anyway.

However, astronomy socities are not just for beginners. Many members of my own society Cranbrook Astronomical Society (CADSAS) are very knowledgeable and experienced.

So, even if you have been observing or studying astronomy or space science for a number of years, then please join and contribute to your local society.

We even have regular contact with professional astronomers in our area, who have been willing to advise us regularly and give talks to our members.

So what are the good reasons for joining an astronomy society?

Access to equipment to try or borrow

Buying a telescope is expensive. Buying add-on accessories like imaging devices and “go-to” computerised mounting and drives, can often be more expensive.

Particularly when you are getting started, it is very easy to spend a lot of money on a telescope and equipment, only to find out when it is too late that it does not fit your needs.

Most societies will have telescopes and other equipment that you can use to get the feel of how it works. You may even be allowed to borrow items to test them at your home, in conjunction with your own telescope.

In this way, you can try before you buy something similar. This should help avoid expensive mistakes.

Special equipment

Some astronomy societies have much larger and more expensive telescopes, than amateurs would typically own. My society for example, is currently restoring a 22.5 inch reflector, housed in a purpose-built observatory.

As a society member, you can get the opportunity to use large instruments like this.

Knowledge and advice

Astronomy societies have many knowledgeable members who are usually, very helpful to other members.

It is a great resource you can tap-in to as a member.

Talks and events

Most astronomy societies will have a programme of events and talks throughout the year.

These give you a good chance to learn new topics and find out about new techniques (eg astrophotography and imaging) from other members, as well as guest presenters.

Summary

All in all, there are many benefits to be had from seeking out and joining your local astronomy society.

I highly recommend it!

Astronomy is the science of studying the universe around us. It uses modern scientific techniques such as measurement, evidence, factual analysis, experiments to test theories, rigorous publication and peer-review.

Astrology is different – it is based on the belief that the positions of the stars, Sun, Moon and planets in the sky, in some way influence events and human behaviour here on Earth. It therefore seeks to analyse and identify what these influences might produce.

Nowadays, astrology and astronomy are quite different, but in years gone by, it was not like that.

Most astronomers I meet now, dismiss astrology as an irrelevance. In fact they rather “look down their noses” at anyone who takes astrology in any way seriously.

But a few hundred years ago, astrology and astronomy were closely related. You could even say that modern astronomy grew out of astrology.

One of the greatest people in astronomical history was Kepler . He developed our modern theories of planetary motion. Yet his work was a curious mixture of astronomy and astrology, as we now understand it.

As part of Kepler’s duties as a university professor, he was required to perform astrological analysis and astrological ideas appear throughout his written work.

It was much the same for other great astronomers of the period.

In those times a few hundred years ago, all the courts of Kings and Princes employed astrologers and they were important positions. Their duties were to analyse the heavens, work out the influences and then assist their masters directly with day-to-day decision making.

Of great importance in astrology are the twelve Signs of the Zodiac. These are the star constellations through which the Sun appears to pass each year, from our viewpoint here on Earth.

Of course in reality, the Sun does not get anywhere near any of these stars. (And there should actually be thirteen constellations, not twelve, because of Ophiuchus!)

Nevertheless, the Signs of the Zodiac can be very useful when talking about astronomy for kids. They all seem to know about the Zodiac and their birth sign, so kids are always keen to find out where “their” constellation is in the sky.

So astrology can be a good way to help kids become interested in astronomy.

This magnitude system was actually first devised by Hipparchus, the Greek astronomer, a long time ago in the second century BC.

It is based on the principle that the stars we can see with the unaided eye, should be classified between magnitude 1 for the brightest and magnitude 6, for the faintest.

Please note that the magnitude classification refers to the apparent brightness of the star as it appears to us, observing from the surface of the Earth. Magnitude figures usually have nothing to do with the actual brightness of the star.

A very bright star a great distance away, could easily appear less bright than a fainter star, much closer to Earth. Magnitude is (usually) not used as a measure of actual brightness.

However, sometimes books will quote actual magnitudes, although this should be clearly stated. You need to watch out for this so you do not get confused.

Back in the time of Hipparchus, magnitudes would have just been judged by eye.

In more recent times, sensitive scientific measurement has been applied to the classification of apparent brighness, but the fundamentals of the system have not really changed.

Magnitude 1 is now defined as exactly one hundred times brighter than magnitude 6. This means that each magnitude number is approximately 2.5 times brighter than the next. So a mag 1 star is 2.5 times brighter than a mag 2 star, and so on.

The faintest stars that people with good, but unaided eyesight can see, are still classified as magnitude 6.

As a consequence, some objects in our sky are so bright that negative magnitudes are needed, if the scale is to remain consistent.

So the brightest star we can see, Sirius, is magnitude -1.4. And the planet Venus is magnitude -4.

Consequently, astronomers usually measure space distances in light years.

One light year is the distance light travels in one year.

Light travels pretty fast – 186,000 miles per second (and according to the theory of relativity, nothing, but nothing, can travel any faster).

A light year therefore works out to be 6 million million miles.

So let us take an imaginary journey from the Sun, riding on a beam of light that has just been created from the nuclear reactions of the Sun

Our light-beam transporter leaves the Sun and heads out into the Solar System.

Let look at how it takes us to get to objects, even when travelling a the speed of light. This may give us some sense of some of the vastness of Space.

We set off from the Sun (and let us assume that all the planets are in a line)… NOW!

After 3 minutes we pass Mercury and after another 3 minutes, we speed past Venus.

It takes 9 minutes in total to reach the Earth, even at the speed of light (so we actually “see” the Sun as it was 9 minutes ago)

Just 1 second later, we pass the Moon.

Then we are heading towards Mars, and reach it 4 minutes later. We have now travelled a total of 142 million miles since we set-off from the Sun.

At 45 minutes into our journey, we reach Jupiter. Gosh! Isn’t it big and red?

Saturn is nearly twice as far from the Sun as Jupiter. On our light beam takes 80 minutes in total to reach it. We fly past Saturn and it also looks big, although not quite as big as Jupiter was.

We continue, on out into the far reaches of our Solar System.

Uranus goes past at 3 hours of travel.

Followed by Neptune at over 4 hours

We might catch a glimpse of Pluto (now no longer thought of as a planet) at around 6 hours, although Pluto has an eccentric orbit and is sometimes inside Neptune’s orbit.

That is the end of our Solar System. We are now heading out into deep space on our light beam.

It is would be sensible to get some sleep now. It is going to take over four YEARS to reach the nearest star!

The nearest star is the alpha Centauri binary star plus its companion, at around 4.3 light years, in the constellation of Centaur.

The brightest star we see from Earth is Sirius in the constellation of Canis Major. It would take us nearly nine years to reach Sirius, even travelling at the speed of light.

So when we look at Sirius from Earth, we see it not as it is now, but as it was, nearly 9 years ago.

Other bright stars we see from Earth are further away. Vega in the constellation of Lyra is 26 light years away, whereas Rigel in Orion is 800 light years distant.

Even at the great distance of Rigel, we are still with in our own galaxy, the Milky Way.

We believe that our galaxy the Milky Way, has a diameter of 100,000 light years.

The nearest galaxy outside our own, is the Andromeda nebula. This can be seen from Earth with the unaided eye, as a fuzzy blob in the constellation of Andromeda. It is the most distant object with can see without a telescope and it is 2.5 million light years away.

So even at the speed of light, it would take us 2.5 million years to reach the nearest galaxy. From Earth, we see the Andromeda galaxy as it was 2.5 million years ago, not as it is now.

It could actually have disappeared for all we know!

Yet to us on Earth, it would look as though it was still there, for the next 2.5 million years.

Other galaxies (and there are countless) are much further for the Earth and could take hundreds or thousands of million years to reach.

Space is big!

But how do you go about choosing a suitable pair of binoculars for astronomy?

I would say that the key advantage of binoculars is their portability and ease of use. Consequently, you are going to want a reasonably lightweight and compact pair. This will rule out binoculars having particularly large lenses, but you will want to get a full-sized pair, rather than ultra-lightweight pocket versions, which usually have inferior image quality.

Let’s get specific and look at the numbers.

Binoculars are usually designated by a pair of numbers such as 8×40 or 10×50.

The first number in the pair is the magnification (or “power”), the second number is the diameter of each main lens in millimeters. So a pair of 8 x 40 binoculars will give a magnification of 8 times and each of the two main lens will be 40mm in diameter.

The bigger the lenses, the more light will be gathered, so enabling you to see fainter objects in the sky. But bigger lenses, mean heavier and larger binoculars.

You can get specialist binoculars having with lenses as large as 100mm, but these are like monsters! For general astronomy use, 50mm lenses are usually considered to be the best compromise.

With magnification, the higher the number the smaller the area of sky will be in the field of view.

You might think that a high magnification is good, but it means the binoculars become much more susceptable to movement in hands or arms, making the image shake. Also, the image degrades if magnification is too high for a given size of main lens. Consequently a magnification of 7 times or 10 times, is usually best.

So we come down to 7×50 or 10×50 binoculars, as being the best choice for general astronomy.

As regards price, you can get a very acceptable pair of binoculars for as little as $60 or £40. I have done this and have been pleased with the results. However you can of course, spend a lot more and get better quality.

The coating on the lenses is important. Higher quality lenses will have better “multicoated” lens. The coatings are intended to reduce internal reflection of light, within the binoculars as this degrades image quality.

Another factor to look for is field of view (FOV). More expensive binoculars may have “wide-angle” eyepieces. These give a wider field of view (for example, 8 degrees rather than 6 degrees), enabling you to see more sky at one time. This is good and makes it easier to see whole star constellations and so learn areas of the sky.

Another important advantage of wide-angle eyepieces is better “eye relief”. This means that your eye does not have to be as close to the eyepiece, to be able to see the full field of view. This is especially useful for spectacle wearers.

If you have the money, you can now get “image stabilized” binoculars. These have a built-in gyroscope mechanism that compensates for wobble and shake, by adjusting the internal optics in real time.

So you can enjoy a steady image, even if the binoculars are moving about somewhat. Image stabilized binoculars also allow higher magnifications, say 12 or 15 times to be used, while still being unmounted and handheld.

Excellent astronomy fun and discovery, can be had with nothing more than a pair of binoculars, plus a little knowledge and a good dollup of enthusiasm.

Binoculars have some great advantages over telescopes,  when it comes to astronomical observation:-

1. Binoculars are totally portable.
You can pick up even a large pair of binoculars, without thinking about it. You can take them easily to anywhere you plan to observe from, be it a friend’s house, your astronomy society meeting, a nearby dark location or even a star party.

2. Binoculars require no set-up.
A telescope it will need to be moved, together with its tripod and associated add-on equipment, to the observing position. It will usually then need to be positioned on a level surface and North aligned. If the telescope has a computerised drive, you will have to make sure the batteries are charged and then go through the initiation and set-up, followed by “training” the telescope drive so it can track and find stellar objects. This can easily take 15-45 minutes.

3. You keep both eyes open when observing.
For some people, this is a huge advantage. I have met many people who find it very difficult to close one eye, while looking with great detail and concentration through the other eye. Binoculars give a far more relaxed experience.

4. It is easy to find objects in the sky, through binoculars.
Yes, this is partly because the magnification is lower than with a telescope, but nevertheless, most find it fairly intuitive to point the binoculars on the small area of sky they want to observe and actually find it in the field of view.

5. Binoculars are not expensive.
My pair of 7×50 binoculars cost only about $60 and they work really well. You can get better quality, of course, but even for a high amateur standard, $200 or the equivalent should be more than adequate.

You should be able to observe many very interesting Night Sky objects with a reasonable pair of binoculars. To help you, I very much recommend my friend Robin Scagell’s book, Stargazing with Binoculars. (see image on the right).

The Moon is always good to look at. Also the star constellations.

The great thing about binocular observing is that you can get a whole constellation in the field of view, in one go. This encourages a nice familiarity with the shapes, which will help you find your way about the sky. Star clusters like the Pleiades are also excellent to view. Plus, many double stars can be easily “split” with decent binoculars.

I hope this article has given you the sense that binoculars can be really enjoyable for astronomy. They can open up the Night Sky easily, for a very small investment.