Should you make your own telescope?

Making you own telescope is often abbreviated as ATM (amateur telescope making) and it has quite a following of enthusiasts.

Great Astronomers Used To Do It

If you read about the history of astronomy, you will see that many of the great astronomers in the past built their own telescopes.

They sought to improve on what was available and also, to build an instrument that was designed for the work they wanted to do.

You can justify a DIY (do it yourself) telescope similarly now. I like the idea of getting a custom solution, together with perhaps getting more for my money.

Also, the idea of creating something with your own hands, that you then use to explore the Universe, is fantastically attractive to me, at least.

But, Times Have Changed?

When I was first getting into astronomy, it was fairly common to make your own telescope. As a teenager, I was tempted to try, although I did not.

Nowadays though, there is a much wider range of good-quality, commercially produced telescopes, available at fairly inexpensive prices.

The industry has been led by a small number of large companies. They have taken advantage of mass-production techniques and manufacture in the currently low-cost area of China, to provide some very good value equipment to amateur astronomers.

So Why Would You Make Your Own Telescope Now?

I know that many keen astronomers would think that you were a bit bonkers, if you announced you were going to make your own DIY telescope today.

They would tell you to go for the good commercially available stuff, I have just mentioned.

Generally, I agree with them.

However, I would suggest there are two situations when it is perfectly sensible to consider the DIY (or ATM) telescope making approach.

These are:

Firstly, if you want a large aperture telescope (say over 12 inches/300mm aperture) and cannot afford thousands of pounds or dollars to buy one “off the shelf”

Secondly, if you would really enjoy the project of creating a telescope yourself and would get real satisfaction, from using an instrument built specially to your requirements.

I personally fall into the second category.

So How Would You Go About It?

So if you decide to give amateur telescope making a try, how would you start?

The first thing is to settle on building a reflecting telescope, based on a mirror, not any other type of telescope. Don’t think about refractors or hybrid designs (for example Schmidt Cassegrains), these use large lenses and are too hard to make.

The most favoured telescope for DIY build is a Newtonian reflector, on a simple Dobsonian mounting. There are many plans available to show you exactly how to go about it.

Then comes the big decision – will you make your own main mirror?

This is exactly what DIY telescope makers always used to do.

The advantage is that you CAN get a good mirror at low cost, by physically grinding and polishing a blank disc of glass into a parabolic telescope mirror.

The disadvantage is that it takes a long time, is a lot of hard work and requires a high level of technical skill to get the correct profile on the mirror surface.

I have to admit, I’ve never made a mirror, but people do and they seem to enjoy the experience.

I would recommend instead, buying a ready-made mirror set. This is a matched pair, consisting of the large main mirror together with a flat secondary mirror, which is what you need make a telescope in the Newtonian configuration.

Commercially-made mirror sets are not too expensive, although the price goes up rapidly with size.

Most importantly, buying a mirror set should ensure that you have high quality optics as the basis of your telescope.

Then you will need to check your plans and make or buy all the various other components and get started!

Here is a simple online spreadsheet to look at the various items and costs involved. ATM Cost Spreadsheet

Summary

It is perfectly possible to build a DIY telescope and many people do.

If you are keen to own a large reflector and would enjoy the project, it can make a lot of sense.

It’s a chance to visit the ancient library of St John’s College and take part in the Sir Fred Hoyle day – one of John’s most successful and remarkable fellows.

The event details are Saturday 8 November 2008, from 11am to 4.30pm, at St John’s College Cambridge (it’s located right in the middle – park nearby and enjoy the short walk through the atmospheric Cambridge streets)

Once there, you can absorb talks and tours of the library.

Also, you will be able to view Sir Fred’s collection of books, childhood records, wartime memories and important astronomical correspondence.

Funded by the National Lottery, it’s an event, not to miss.

PS..

Entry is free.  More details here

Kings College Cambridge, plus punts on the river

Blessed with beautiful sunshine today, I travelled to Cambridge for the 2008 Convention of the Federation of Astronomical Societies.

On arrival, I found represented a good selection of astronomy equipment retailers, specialist organisations and astronomy societies.

Plus, a very interesting programme of talks in the IOA lecture theatre.

Dr Barry Jones (Open University) was particularly good on “The Search for Extra-Terrestrial Life”. As was Prof, Andy Fabian on the “Power of Black Holes”.

Barry Jones speaks to the lecture theatre on the search for ETI

There was also a tour of the historic telescopes the IOA has on its “Observatories Site”, such as the Northumberland telescope.

This is the most historic telescope they possess. It was commissioned for the newly-formed University Observatory in 1833 by the Duke of Northumberland, hence it’s name.

As an 11.6 inch refractor, it was then one of the largest in the World. It was installed with great care and precision by the then Director of the Observatory, George Airy (of “Airy disc” fame).

The Northumberland is the famous telescope which “almost” discovered the planet Neptune, under the guidance of Prof. Challis. However, the discovery was not recognised and another astronomer published first.

Today, the telescope is largely in it’s original condition, although the objective lens was replaced a few years ago with a slightly larger, 12 inch lens. Also the original wooden dome was replaced some decades ago, with the current metal item.

Northumberland Telescope Observatory

The Northumberland is still in regular use today. Indeed on most Wednesday nights, you can use it yourself, as it is made available for the public observing sessions, which are held there.

Northumberland Telescope From the Observer’s Viewpoint

The telescope tour also included the Thorrowgood 8 inch f14 refractor…

Thorrowgood Telescope

And finally, the 17 inch Schmidt, made in the 1950′s. It is not used very much now, because of light pollution in Cambridge city, but may soon be transferred to an observatory elsewhere in UK.

Schmidt 17inch Telescope, No Longer In Use

All in all, a very interesting day and an chance to discuss astronomy with like-minded people.

Neptune is the furthest out of the “Gas Giant” planets and is right out at the limits of our Solar System, 2800 million miles from the Sun.

The story of its discovery is fascinating…

Neptune

Neptune’s existence was suspected long before it was actually discovered.

Astronomers in the early 1800′s found that they could not reconcile the observed position of the newly discovered planet Uranus, with the position they expected through calculations.

So some astronomers began to suggest that perhaps there was an undiscovered planet in the same area of the Solar System, that was affecting the orbit of Uranus.

Various people became involved in the search for the new planet. Notably, these included a young French mathematician called Urbain Le Verrier and a young English mathematician called John Couch Adams.

Both of these men calculated where in the sky, they would expect Neptune to be found. Adams did not publish his work, but Le Verrier did by means of two notes, in 1845 and 1846.

The search to find Neptune observationally began.

John Challis, Professor of Astronomy at Cambridge, used the Northumberland 11.6 inch refractor but did not find it.

(Incidentally, this telescope can be visited and is still used at the present time, in Cambridge. I have seen it and it is a wonderful piece of astronomy history)

Reviewing the episode later, after the new planet had been discovered, Challis found that he had actually seen and recorded Neptune almost immediately in the predicted position, but he had not realised it. I bet he was cross!

Meanwhile, Le Verrier had sent his calculations and predictions to Johann Galle at the Berlin Observatory.

With this valuable information, Galle looked and found very quickly. Neptune was discovered on his first night’s observation in 1846.

Later, it was discovered that Adams had also been correct with his predictions of Neptune’s position, but unfortunately, it had just taken too long for the English astronomers to follow it through to the observation stage.

Neptune is not actually that difficult to see with a telescope, if you know where to look and what you are looking for.

Through a telescope, the Neptune’s disk looks blue. Like Uranus, this is due to light absorption by methane.

Neptune is also very similar in size to Uranus.

The largest of Neptune’s moons, Triton was discovered soon after the planet itself in 1849, but the second moon, Nereid, took much longer (1949). It is close to the planet and hard to see.

The most significant recent event was the Voyager space mission. It flew past Neptune in 1989.

Voyager found six additional satellite moons, together with a faint ring system – another similarity with Uranus.

However Neptune does not share Uranus’ extreme axial tilt. Neptune’s axis is inclined at just 29 degrees to the plane of the orbit. Only a few degrees more tilted than Earth.

Voyager also succeeded in measuring the period of rotation. Neptune’s “day” was found to be 16 hours 7 minutes long.

He was initially a successful musician, but then began to concentrate on his hobby of astronomy.

Over the course of the next fifty years, he become the greatest telescope-maker of his time and quite possibly, the greatest observer ever.

The big achievement he is now most often remembered for, is his discovery of the planet Uranus in 1781.

He did this with his home-made telescope. It was the first ever planet discovered by telescope…

William Herschel said of himself, “I have looked further into space than any human being did before me”.

He also encouraged his sister Caroline Herschel and his son John Herschel, to become successful astronomers.

William Herschel was originally from Hanover in Germany, the son of a musician.

Born in 1738, he found himself in 1757, in the army and fighting the French, after they had invaded Hanover.

He deserted and escaped to England.

He began to work as a musician and in 1766, was appointed to a prestigious position as organist at the Octagon Chapel at Bath.

At this time, Bath was a very fashionable resort for high society. William’s Hanoverian origins were probably an advantage, with George the third as King.

His sister Caroline joined him as housekeeper and assistant in 1772 and it was from his house in King Street, Bath that he began to practise astronomy.

He began to make his own telescopes, being dissatisfied by those that were available at the time.

Herschel made reflecting telescopes, using a mirror to gather light, instead of the more usual lens. He made his own mirrors from a very hard alloy of copper and tin called “speculum”. He somehow worked out a way of polishing the hard surface into a reflecting surface of the correct profile to give a good image.

Two things resulted from the telescope making expertise he had developed. Firstly, Herschel was able to observe and map the sky in unprecendented detail. Secondly, his telescopes became sought after and Herschel went on to make a lot of money from the building of telescopes.

Caroline played an important part in this work. She was closely involved in the telescope making and also the observation work.

His big breakthrough came in 1781 when he discovered Uranus. He became famous and was summoned to visit King George III, to demonstrate his telescope and explain the discovery.

As a result, the King appointed Herschel as his own astronomer, with a salary for himself and his sister Caroline, plus a house at Slough (near Windsor) which was to be set up as an observatory.

He also pardoned him for desertion from the army.

There at Slough, William built his largest telescope which had a 48 inch mirror and a focal length of 40 feet.

For more than thirty years, the Herschels continued with their meticulous work on the night sky.

They sent countless papers to the Royal Society, cataloguing and describing the objects they had observed.

For example, the Andromeda Galaxy (which is our nearest-neighbour, spiral galaxy and the furthest-away object you can see with the unaided eye) is referred to as M31.

The Messier Catalogue

M33 Triangulum Galaxy

These M numbers come from a catalogue of celestial objects that was created by the French astronomer Charles Messier, in the 1700′s and early 1800′s.

Messier was primarily a comet hunter. He was employed by the French authorities and given the task of finding Halley’s Comet, when it was expected to return to near the Earth in the late 1750′s.

Messier duly detected Halley’s comet as it returned. He also discovered about 20 other comets, during the course of his observing career.

While searching for comets, Messier kept a list of objects in the sky which might confuse a comet hunter. These were fuzzy objects that looked rather like comets, but which did not move across the sky in the way comets do.

Each of these comet-like objects was given a number, hence the Messier (or M) numbers.

Hence, the Messier Catalogue came into being and this is what Messier is remembered for today, not his comet hunting.

We know today that the Messier objects are a collection of star clusters, nebulae and galaxies.

You should be aware that there are other catalogues of similar objects.

Most of the Messier objects also have other classification numbers, from different catalogues. This can be confusing.

In addition to M numbers, there are also the commonly-used “NGC” numbers. These refer to the “New General Catalogue of Nebulae and Clusters of Stars”, which was drawn-up by the Danish astronomer Dreyer, in 1888.

So for example, the Andromeda Galaxy M31, is also classified as NGC 224.

Observing the Messier Objects

The Messier objects are some of the most interesting objects for amateur astronomers to search out and observe in the sky.

Messier’s catalogue contains 110 objects.

Some well-known examples are:-

M1, the Crab Nebula, in the constellation of Taurus
M42 and M43, which together make up the great nebula in the constellation of Orion
M51, the Whirlpool Galaxy, in the constellation of Canis Venatici
M57, the Ring Nebula, in the constellation of Lyra

The “Messier Marathon”

Nowadays, some observers attempt what is known as the “Messier Marathon”.

This challenge is to observe as many objects from the Messier catalogue as you can, in one night. The target of course, is all of them!

This is just about possible, although only at certain times of the year and from northerly latitudes.

As the Messier catalogue was compiled from the Northern Hemisphere, some of the objects are very difficult from the Southern hemisphere as they are very low in the sky.

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.

But he undoubtedly improved the telescope and was the first to use it for astronomy, making several hugely important discoveries. But before that, let us look at how it all started for him.

Galileo was born into a noble family in 1564.

It might have been noble, but his family was not wealthy. Galileo would need a profession and it was decided by his father that it should go into medicine.

He started at the University of Pisa, and his studies went well but in addition to medicine, he became very interested in mathematics and geometry.

He got a private tutor but his father became worried he was neglecting his medicine studies and the tutor was dismissed.

Nevertheless, he was recognised as a brilliant student.

The university authorities admired his thirst for knowledge, but even at this early stage, they also disapproved of him.

Galileo was already starting to questioning the established laws of nature, as determined by Aristotle and Ptolemy, over a thousand years previously and now established as doctrine.

At this time, he created his first invention and it was an important one. This invention alone, would probably have been enough to justify his subsequent fame.

We now take for granted, pendulums in old clocks. Galileo invented the pendulum method of regulating a clock, after apparently watching a swinging chandelier!

His talents were duly recognised and he became Professor of Mathematics at Pisa university when he was just 25 years old.

With his new stature as a professor, Galileo began to openly question the dogma of Aristotle’s laws on nature.

He was particularly critical of Aristotle’s “law” that heavier an object was, the faster it fell if it was dropped. Galileo decided to prove this wrong.

He did this in a particularly public way, by carrying out an experiment on Tower of Pisa, in front of a huge crowd. He dropped a heavy object and a light object, together and they both hit the ground at the same time.

This was his first important step in dismantling the ancient system of dogmatic rules that was holding back scientific development.

However, his problems started. His robust attitude and these challenges to the scientific establishment, caused him to fall out with the authorities.

Under sustained pressure, he had to leave Pisa and the university. Fortunately, he manged to secure a position in the university of Padua, again as professor of mathematics.

Here in Padua, Galileo’s important work on telescopes and astronomy would be done, as I describe in Galileo’s Telescopes And Discoveries

By the time he was 28 years old, he was at Padua University, holding his second Professorship of Mathematics. He had unfortunately needed to leave the university of Pisa and his Tuscan homeland, having already upset the authorities there.

Here in Padua, he was to start the work that was soon to revolutionise science.

Galileo so loved inventing equipment to help his work, that he had a skilled instrument maker live with him at his house.

So when he found out about the very first telescopes being made in Flanders, he started to make his own telescopes and improved them.

He was also clever enough to demonstrate his telescopes for important people. He gave away many as gifts, to those people with influence around Venice.

Galileo used his new telescope himself, of course.

With it, he was able to see many thing that were obviously inconsistent with the classic Aristotle view of the perfect universe, with everything revolving around the Earth.

He saw that the Moon was cratered and the Sun had spots on it – both less tha “perfect”.

He saw that the Milky Way was composed of countless stars, made visible simply by using the telescope. These must be further away and not stuck to the same “crystal sphere”, at the same distance from Earth, as the stars that could be seen unaided.

Then there was the most significant discovery – he saw four moons clearly orbiting aound Jupiter.

These astonishing views he saw through his telescope, made it clear to Galileo that the heliocentric (Sun-centred) model proposed by Copernicus some sixty years earlier – the model that had received such vehement opposition from the Church and authorities – was likely to be the true one.

Interestingly, Galileo’s telescope was not good enough to see the rings of Saturn with any clarity. He recorded that Saturn had a blob on each side…

But if any evidence is needed that his observations were meticulous, then his discovery of the libration of the Moon surely provides it. We are familiar with the fact that the same side of the Moon is always faces the Earth. The libration phenomenon is a slight variation in rotation that lets us see sometimes slightly more to the east, west, north or south of the surface than usual. You have to observe very carefully to notice this.

Galileo first got into trouble with the Holy Roman Church, shortly after the Church condemend Copernicus’ book as heresy in 1616.

It was suspected (with good reason,) that Galileo was promoting the Copernican ideas that the Earth went around the Sun. Galileo, himself a devout Catholic, was forbidden to teach or promote any of this heresy.

Some years passed and he had favourable contact with two successive Popes and felt that attitudes were changing.

He went ahead and wrote his most important work, “The Dialogue Of The Two Systems”. This examined the evidence in favour of both the Earth-centred system and the Sun-centred system.

He sent it to the Church for review and after many years delay, received permission to publish in 1632.

Unfortunately, Galileo’s problems really begun at this point.

In October 1632, he was summoned to the Inquisition in Rome, charged with heresy. This was rather serious! He attended in 1633.

When he arrived, it could of been made a lot worse for Galileo. His powerful friends helped him. He was allowed to stay at the house of the Tuscan ambassador, rather than in prison.

But his book, the Dialogue, was condemned. He had treated the question of the Earth and its motion, as a subject for discussion, when it was not. He had also slanted the arguments in favour of the Sun-centred model, which was at odds with Church doctrine.

He was therefore strongly suspected of heresy.

He had to be punished.

Galileo was forced to swear he would never speak or write again, about the Copernican model which said the Earth orbited around the Sun.

He was also imprisoned, although this was interpreted leniently as solitary house arrest.

If a supernova occurs in our own galaxy the “Milky Way”, it can be highly visible in our sky, sometimes even during daylight.

There have been a number of well-known, highly visible supernova events in the history of astronomy, although there has not been one for 400 years.

When they have occured, they have had great influence on astronomers and astronomical thinking, at that time.

Here is a brief catalogue of known, bright supernovae.

Year AD1006 in the constellation of Lupus

This would have been too low in the sky for the UK, but it was observed and recorded in China and also at St Gallen in Switzerland.

It was very bright – nearly as bright as the Moon – and lasted for over two years. The remnant is not visible optically today, but is detectable as the radio-wave source SN1006.

Year AD1054 in the constellation of Taurus

The remnant is visible today as the Crab Nebula. The exploding star reached magnitude -4 (as bright as Venus appears) and lasted for 21 months.

It was extensively observed and recorded in China, but strangely, there is NO confirmed record in Europe.

We may ask, why was this event ignored? Astronomers surely must have seen it?

It is suggested that to blame, could be the dominant doctrine on the perfection and unchanging nature of the universe, as decreed by Aristotle and Ptolemy a thousand years before. Astronomers were not willing to record what they saw, because it was clear evidence that the universe was not as was believed and they feared upsetting the authorities.

Year 1572 in the constellation of Cassiopeia

This was the supernova that was famously observed and measured by Tycho Brahe. It made his reputation as a great astronomer. It also touched him personally, writing that it was “a special creation of God”. Tycho’s personal notes still exist in a museum in Copenhagen.

It was as bright as Venus (about mag-4), but by May 1573 has faded to magnitude 2. Today, its remnants may be found in the optical and radio spectra.

Year 1604 in the constellation of Ophiuchus

This supernova is often known as the “Kepler Star”, not because Kepler discovered it, but because he observed, measured and recorded it as part of his official work.

It was like as bright as Venus, like the one of 1572, just 32 years before. But particularly striking, would have been its proximity to both Jupiter and Saturn, at that time. A remarkable sight!

When will the next “guest star” appear in our galaxy?

Who knows? Certainly not me. But 400 years have passed since the last nearby star explosion.

And we have recently detected hundreds of supernovae in other galaxies.

So perhaps it will not be too long to wait?