Deep Sky Section Meeting 2002 - Meeting Report

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The Deep Sky Section's popular annual meeting was this year a rather special one, as it marked the Section's twentieth anniversary. Bob Marriott welcomed the audience on behalf of our hosts, the Northamptonshire Natural History Society, of which he is President.

Directors Report

In his Director's Report, Nick Hewitt said that the jewel in the Section's crown continued to be supernova discoveries. By the date of the meeting five observers - Ron Arbour, Mark Armstrong, Tom Boles, Steve Foulkes and Stephen Laurie - had between them discovered 31 supernovae from British soil since 1996. (A mere two days after the meeting, Mark Armstrong found his nineteenth supernova!) Taking a longer view, Dr Hewitt said that the Section's first two decades had seen huge changes in deep-sky observing, the main cause being the rise of computers and the Internet. On the professional side, the spectacular images taken by David Malin and the Hubble Space Telescope both made their mark in this brief era. A less happy aspect was the persistence of light pollution and a consequent decline in visual observing. Looking forward to the next twenty years, Dr Hewitt predicted that the quality of CCD images would continue to improve and that there would be more astronomical 'tourism' by amateur astronomers trying to escape the light pollution.

Karen Holland - Brown Dwarfs in Praesepe

The first main speaker was Karen Holland, a BAA member who had taken part in a project run by Leicester University to look for brown dwarfs. Mrs Holland and the Leicester team chose the Praesepe star cluster M44 in Cancer for their search. Brown dwarfs are best looked for in clusters, because they are very faint and hard to identify in the sky as a whole. The stars in a cluster are similar to each other in a number of ways and so brown dwarfs should stand out. The plan of the Leicester team was to identify possible brown dwarf candidates by measuring the motion and mass of every star in the cluster.

The team's calculations assumed that the cluster was symmetrical. To check this, they did a plot showing the density of stars in the cluster and to their surprise found what appeared to be a small sub-cluster to one side of Praesepe that seemed to be merging with the main group. X-ray observations by other astronomers seemed to confirm its presence. Further calculations showed that Praesepe seemed to be flying apart and will probably disperse within about 10 million years.

A paper describing their discoveries has been accepted for publication, but much more work needs to be done before the cluster merger can be confirmed. In the meantime, no brown dwarfs have yet been found in the cluster, although another team has found a white dwarf that may be a member of the sub-cluster.

Mark Armstrong - UK Supernova Patrols

Next to speak was Mark Armstrong, who talked about the efforts of British amateurs to discover supernovae. Mr Armstrong began patrolling for supernovae using a CCD camera attached to his telescope in June 1995 and became the first person in the UK to discover a supernova in October 1996. The following year Steven Laurie and Tom Boles joined the ranks of supernova discoverers, and Ron Arbour made his first find in April 1998, after a heroic 20 years of searching. Steve Foulkes became Britain's fifth supernova discoverer in January 2000.

To increase the potential for discoveries it is necessary to be able to image down to fainter magnitudes and so the supernova hunters have constantly upgraded their equipment over the years. In 1999 Mr Armstrong upgraded to a 12-inch Meade LX200 telescope and a Hale Research camera and more recently added a 14-inch Celestron, a robotic mount made by Software Bisque and an SBIG ST-9 CCD camera to his equipment arsenal. With these two telescopes running automated patrols for supernovae at the same time Mr Armstrong now averages 600 hours of patrolling a year. He is confident that he can stand up to the heavy competition for discoveries by professional and amateur astronomers in the USA who are working in far better weather conditions than in the UK.

Lunch

The Section then celebrated its twentieth anniversary with an excellent cheese-and-wine lunch kindly provided by members of the Northamptonshire Natural History Society. Members also had the chance to view an exhibition of the Section's work over the past 20 years, which included some beautiful paintings by John Lewis.

Ron Arbour - History of the Deep Sky Section

The retrospective theme continued after lunch when Ron Arbour, the Section's founder, talked about how the Section was formed in 1981. When Mr Arbour joined the BAA in the 1970s, the observing sections were strongly orientated towards visual observing of the Solar System and variable stars. Mr Arbour was a keen astrophotographer, but when he suggested starting an astrophotography section within the BAA this was opposed by the section directors of the time. He then suggested that a deep-sky section be formed and, although there was still some opposition, he was eventually successful.

Working with a few helpers, Mr Arbour put together the first edition of the Section's newsletter, Deep Sky Diary. Word processing and desktop publishing still lay in the future in 1981 and a professional typist was paid to produce the copy. The section quickly became one of the most popular in the BAA, its membership rising to 200 in 18 months. Mr Arbour was also proud to watch the quality of observations rise in the ensuing 20 years.

Nik Szymanek - CCD imaging from La Palma

The second afternoon speaker was Nik Szymanek, who spoke about CCD imaging from La Palma in the Canary Islands. Mr Szymanek and his friend Ian King have for several years made regular trips out to La Palma with their telescopes in order to escape the light pollution of their native Essex. They have become well known as pioneers of CCD imaging and have specialised in tricolour or RGB (red, green, blue) imaging, in which exposures made through red, green and blue filters are combined to produce a single colour picture. To take their images they use a 10-inch Meade LX200 Schmidt-Cassegrain telescope and an SBIG ST-7 CCD camera fitted with a special adaptive optics system to cancel out small guiding errors.

He also showed some images taken using a technique known as 'LRGB' that they have developed along with several other amateur astronomers. One problem with colour CCD imaging is that the resolution is never as good as monochrome. In order to get around this Mr Szymanek and several other amateur astronomers have together invented a new technique in which a fourth exposure known as a 'luminance' image is taken in black and white at very high resolution and added to the stack of red, green and blue images. The technique has become known as the LRGB technique, with the 'L' standing for luminance. The result is the best of both worlds - a colour image with the resolution of black and white. Mr Szymanek showed a number of images of various deep-sky objects taken using this technique and they were a vast improvement on colour images taken several years previously.

Recently Szymanek and King had become involved in processing professional images taken using the Jacobus Kapteyn, Isaac Newton and William Herschel telescopes on La Palma. The aim was to produce high-quality images for the observatory's public relations activities. Using Maxim DL image processing software they have produced some stunning results. One particularly memorable image of M51 in Canes Venatici won them funding from the observatory for further public relations work.

Owen Brazell - New Challenges in Planetary Nebula Observing

Switching to the visual side of deep-sky observing, the next talk was by Owen Brazell and was titled 'New Challenges in Planetary Nebula Observing'. The recent appearance of many Hubble Space Telescope images showing unprecedented detail in planetary nebulae was inspiring some advanced visual observers to look for some of this detail through the eyepiece. The equipment required for this work breaks away from the tradition of 'light-bucket' telescopes and low magnifications for deep-sky work and bears more resemblance to that used for planetary observing: high magnifications, very good optics and a driven mount. There has also been a recent trend towards hunting for planetary nebulae in globular clusters, such as Pease 1 in M15 and GJGC1 in M22. These objects are very small and extremely hard to identify from the thousands of surrounding stars.

Planetary nebulae are still being discovered, a recent example being an extremely faint one found photographically by Brian Skiff of Lowell Observatory. However, some of the claims for visual sightings of faint objects by amateurs are becoming ludicrous. For example, some amateurs have claimed to see nebulosity where nothing is shown on Palomar Observatory Sky Survey plates! Observers need to bear in mind that nebula filters can give the impression of nebulosity surrounding stars. Also, some people are claiming that seeing an object just 5 per cent of the time they are looking at it is valid detection.

Martin Ratcliffe - Message from America

Following the afternoon tea break there was a short video presented by former Deep Sky Section Director Martin Ratcliffe, congratulating the Section on reaching its twentieth birthday. Martin now works in the USA where he directs a major planetarium complex in Wichita, Kansas.

Alan Dowdell - The Whirlpool Galaxy, M51

Another leading light in the Section's early days, Alan Dowdell, then gave a talk on his favourite deep-sky object, the Whirlpool Galaxy M51. This galaxy is a popular astronomical symbol and, indeed, it was used on the cover of the first issue of Deep Sky Diary. The galaxy was first observed by Charles Messier in 1773, and he also detected its companion galaxy NGC5195, describing the pair as being like two atmospheres almost touching. In the early nineteenth century Sir John Herschel noted that the main galaxy was surrounded by a ring, but it was in 1845 that Lord Rosse saw the galaxy's spiral structure for the first time, using the great 72-inch reflector at Birr Castle in Ireland. As early as this time Admiral Smyth speculated that it might be a great island of millions of stars.

Mr Dowdell commented that over the years the galaxy's spiral arms have been resolved with progressively smaller telescopes. In the mid nineteenth century it took a 72-inch telescope to see the spiral structure for the first time. As recently as the 1960s, drawings made using 30-inch apertures showed the arms only subtly. But nowadays amateurs routinely record them with 10-inch telescopes and visual sightings of them have even been claimed with just a 4-inch refractor! Mr Dowdell concluded his talk with a series of his own sketches showing the appearance of M51 through different-sized telescopes. One particularly striking drawing was made using a 1-metre telescope at Puimichel in southern France.

Nick Hewitt - Variable and Bipolar Nebulae

The last main talk of the day was given by Nick Hewitt and was on the subject of variable and bipolar nebulae. Variable nebulae - of which the best-known example is Hubble's Variable Nebula, NGC 2261 in Monoceros - show noticeable changes in their brightness and structure, sometimes over periods of only weeks. Bipolar nebulae show lobes of material on either side of a central star. NGC 2261 may be a bipolar nebula, but one side of it is thought to be obscured by dark nebulosity. The nebula is illuminated by the variable star R Monocerotis and dust clouds moving around this star are believed to be the cause of the changes in the nebula's appearance. Recent images by UK amateur Steve Goldsmith showed significant changes in the nebula's structure within just one month.

Dr Hewitt announced that he was planning to put forward a project to observe this object and other variable nebulae using the 2-metre Liverpool Telescope which was currently being built on La Palma and on which amateur astronomers could get up to 5 per cent of the available observing time. The Liverpool Telescope could also be used to examine other nebulae for possible variability.

Presentation

Before the meeting ended, Bob Marriott officially presented a 4-inch refractor formerly belonging to the late George Alcock to Denis Buczynski - in absentia, as Mr Buczynski was unable to be present at the meeting. The audience applauded warmly at the handing down of an instrument from one dedicated observer to another. It was a fitting conclusion to a well-attended meeting, which proved that the Deep Sky Section was thriving at the end of its first twenty years.

Lee Macdonald
Secretary