To study and encourage popular interest in all branches of Science.

Newsletter April 2009

Dear Member,

Important Announcement

The next two meetings cannot be held in the Crypt Room at St John's Church as it is currently being redecorated. They will instead be held in a room at The Age Concern (Camden) Resource Centre in Prince Arthur Road, a turning off Fitzjohn's Avenue, NW3. It's only a couple of hundred yards away.

The last lecture this session is at 8.15 pm on May 21st by
Dr Peter Grindrod (Dept of Earth Sciences, University College London) on:
"Water on Mars: Where should we be looking?"

ANNUAL GENERAL MEETING on Thursday June 25th at 8 pm.

This will start with wine and cheese (£2 each) and the AGM itself will start at 8.45 and if time allows will be followed by a scientific Call My Bluff.

The agenda will include the usual reports from Officers and Sections and the Election of Officers and five Ordinary Members of Council for the coming year. Council proposes the following:

Secretary Julie Atkinson
Treasurer & Membership Secretary John Tennant
Programme Secretary Jim Brightwell
Ordinary Members (max 5) Hemant Desai Elizabeth Davies
Nayna Kumari Leo McLaughlin

Council invites further nominations to the above posts and ordinary members; such nominees shall be duly proposed and seconded and have agreed to serve if elected.

A specific item on the agenda will be a proposal by the Council to appoint Professor Robert Weale to be a Vice President and Honorary Life Member.

Summer Visit. A Summer visit by the Society to the Royal Greenwich Observatory on Bank Holiday Monday the 4th May has been organized by Hemant Desai. Details have been put on the web site in view of the short notice:



Doug Daniels

This year, astronomers are celebrating the 400th anniversary of the invention of the telescope and next year we at HSS will celebrate the centenary of our own observatory; so we have been around for a quarter of the time and in that 'last quarter' we have witnessed discoveries that have totally changed our perception of the Universe. These discoveries have been made possible by the evolution of telescopic optics and observational and imaging techniques all of which have seen gathered momentum in the last two decades culminating with the launch of the Hubble Space Telescope in 1990. Hubble at last gave astronomers their first opportunity to make observations unhindered by the Earth's troublesome atmosphere. The fact that it was initially placed into orbit with a defective mirror was soon forgotten once a corrector was fitted and for the last 18 years the results obtained have been truly staggering and exceeded all expectations.

Who can forget the fantastic images such as 'The pillars of creation' - actually the 'Eagle nebula' showing star formation. Or the evolving star V838 Monocerotis, or the one million pixel image of the Orion Nebula, showing dusty disks surrounding young stars - literally nascent Solar Systems. Hubble also showed us the fantastic beauty of planetary nebulae, the Cat's Eye, the Tea Tray and the Spirograph nebulae. But apart from the stunning images available free to all, Hubble has provided astrophysicists with masses of hard data in almost every aspect of astronomical research. The life cycle of stars, Black Holes, Gravitational lensing, Galaxy evolution and the distribution of gas in the Universe and refining distance scales via stellar parallax are but a few subjects from a list too long to quote in full. But to me, the outstanding image is the Ultra Deep Field image, a three-month exposure on a seemingly blank region of space that revealed countless galaxies in full bloom 13 billion years ago when the Universe was just 5% of its present age. Now to put all this into perspective, let us remind ourselves of some of the milestones encountered along our 400 year journey of discovery.

Astronomy is a very visual science. Everything we know or think we know about those remote sparks - the stars or the less remote moon and planets, has been obtained by systematic observations and records made over long periods of time by dedicated observers. For thousands of years, these observations were made with the naked eye and although we can still admire the results and marvel at the surprising accuracy of the work carried out by our ancestors using nothing more than cross staffs, quadrants and astrolabes, it was the application of the telescope to the night sky that made all the difference and elevated astronomy to the status of a proper science by divorcing it from its mystic astrological antecedents. Although such luminaries as Kepler were still not averse to earning a few extra quid by producing the odd astrological chart, if asked.

History tells us that the telescope was invented by a German optician - Hans Lippershey, who was working in Holland around 1608. Lippershey attempted to patent the invention, but his application was not allowed as there was evidence of a predecessor. This seems very likely as we now know that the English explorer Thomas Harriot was using some sort of telescope at about this time and he was making drawings of the moon with it. Harriot's telescope was a gift from a friend, it was described in his writings as a 'Dutch Trunk', so Holland seems to have been the epicentre of telescope production in the early 17th century. It has always seemed strange to me, given the relatively simple optics involved, that the telescope was not invented centuries earlier. After all glass had been around for 3000 years and lenses from at least Roman times.

It was, however Galileo Galilei who made his own telescope and was the first person to apply it systematically to the study of astronomy, beginning in January 1609. In just a few months Galileo had clocked up a record of observational 'firsts': Craters and mountains on the moon, Jupiter's 4 main satellites, Venus' phases, Sunspots, hordes of stars in the Milky Way, Saturn's 'handles' - he didn't figure that one out but who would have at that time? Well, in fact Huygens did from his observations made a few years later in 1655. By this time telescopes were already showing distinct improvement. Huygens got rid of the concave eye lens and made a proper eyepiece consisting of two plano-convex lenses. This meant that from then on astronomical telescopes produced an inverted image but this was a small price to pay for increased definition and a better field of view.

Galileo's telescope was a very primitive affair. It used a simple plano-convex lens as an objective and a plano-concave lens for the eyepiece. Such a combination is only seen today in low power opera glasses. It would have provided a small field of view and bright images would have been fringed with false colour. Eliminating this 'chromatic aberration' was to occupy the minds of telescope makers for many years. In an attempt to reduce it, telescopes with monstrous focal lengths of 100 feet or more were constructed and even Isaac Newton declared the problem insoluble so in 1668 he went off to invent the reflecting telescope instead. But like many problems in science, given enough time and thought, a solution will often present itself. In 1758 John Dollond invented the compound achromatic object glass based on the earlier work of Chester Moor-Hall. Thanks to them and to Newton, astronomers now had two types of telescope to play with, the refractor and the reflector.

Initially, reflectors used mirrors made from speculum metal, an alloy similar to bronze. The early 18th century saw the construction of some really large telescopes, it was the age of the Herschel's following William's discovery of Uranus in 1781, the first 'new' planet to be discovered and by an amateur astronomer observing from his back garden with a home-made telescope. Metal mirrors soon gave way to glass thanks to the work of Liebig, Steinheil and Foucault who demonstrated a method of chemically depositing a film of silver to the surface of glass. He also invented the Foucault 'knife edge' test for concave mirrors in 1851, which might have saved NASA a whole load of trouble had it been applied to the Hubble mirror before its launch in 1990!

In 1845 the biggest telescope in the world resided between two huge brick walls in a field in Ireland. The 72-inch reflector built by William Parsons the third Earl of Rosse at Birr Castle revealed spiral structure in certain nebulae. Just a year later in 1846, Galle and D'Arrest discovered Neptune at the Berlin observatory. Then at the middle if the 19th century, photography made its tentative debut. In 1882, David Gill's photograph of the Great Comet of that year also revealed many star images and paved the way for star mapping using photography. A few years earlier in 1862 Thomas Cooke of York completed the 25-inch Newell refractor which was at that time the biggest refractor in the world but by 1897 the Yerkes refractor in the USA took the title and still holds it! At 40-inches, refractors had got as big as they were going to get; from now on the worlds largest telescopes would be reflectors and most of them would be in the USA.

The nineteenth century in England was a time of rapid industrial and scientific expansion and a time that saw the foundation of the Royal Astronomical Society and The British Astronomical Association. Astronomical discoveries were coming in thick and fast and a lot of them made by amateurs. This was the era of the skilful amateur mirror maker. Men like Calver, With and the Rev.W.E.Ellison produced telescope mirrors of unsurpassed optical quality whilst the UK professional instrument makers: Grubb Parsons, Cooke, Troughton & Simms, Adam Hilger, Wray & Browning tended to concentrate on refractors.

This then was the period in history when the Hampstead Scientific Society was founded - in 1899. Astronomy has always featured strongly in the Society's activities and just a few years after its foundation saw the erection of the Observatory in 1910. In the early years the Observatory site was dark and it was still possible to make original observations. Sadly, light pollution today prevents this but we still open to the public regularly during the winter months and we are proud of our small contribution to the massive bank of data that began to accumulate in Italy in 1609 and has continued to expand almost exponentially ever since.

The twentieth century saw the construction of the World's largest telescope the 200-inch Hale telescope at Mt. Palomar in the USA but it wasn't long before the Russians topped it with a 300-inch. Then began the serious 'Space race' that saw unmanned space probes sent to all parts of the Solar System even to Halley's comet and culminating with the USA manned Moon missions of the 1960's. But the great telescopic achievement of this time was the launching of the Hubble Space Telescope in 1990.

Now at the dawn of the 21st century, astronomical telescopes have progressed to such a degree of sophistication that even the humble amateur can own a robotic instrument that can automatically locate several thousands of celestial objects. Using computers and the Internet, astronomers can manipulate telescopes thousands of miles away and direct them to secure images. Imaging using conventional film has been largely superceded by digital CCD cameras and amateurs can produce images with small telescopes equivalent or better than those obtained by professional observatories two decades ago.

And what of the professionals? They are now using multi-mirror telescopes, telescopes of enormous aperture using light-weight mirrors, dual instrument optical interferometers and adaptive optics that can neutralize the adverse effect of the Earth's atmosphere. Plans are afoot for the European Extra Large Telescope with a 30 metre aperture and for OWL - the Overwhelmingly Large Telescope, originally proposed to have a 100 metre mirror, but since scaled down to half that size. Still orbiting far above is the Hubble telescope, shortly to receive new instrument packages to extend its working life and there are plans for a new orbiting telescope 40 times as powerful as Hubble to ultimately replace it.

Galileo could not have imagined in his wildest dreams what he was setting in motion when he pointed that tiny crude telescope towards the night sky just 400 years ago.


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