On 12 October 2012, the Astronomical Society of South Africa (ASSA) began their 9th biennial symposium, hosted by the Cape Centre of ASSA at the offices of the South African Astronomical Observatory (SAAO). Although it officially began on Saturday the 13th, there were a few extra activities lined up for the Friday as well, for those ASSA members who arrived early. These were an astrophotography workshop hosted by Dale Liebenberg, a free show at the Iziko Planetarium, and a social Braai to welcome the visitors.
The first speaker was Doctor Justin Jonas of SKA Africa, and Rhodes University, and he spoke on the topic of the Square Kilometer Array telescope. He began by explaining the scope of the work currently being done by SKA Africa, such as the conversion of old radio telescope dishes across Africa into radio telescopes, and the builing of astronomy centres across the continent. He also gave a history of South Africa’s SKA bid, from when the idea was first considered up to the eventual site decision earlier this year. Having established this background, he then went into detail on the MeerKAT telescope which serves as an SKA precursor project and will eventually be incorporated into the SKA core. MeerKAT’s location, roughly between De Aar and Calvinia, was chosen for its exceptional radio silence and relatively easy access to power and transport infrastructure. What gives this place it’s unpolluted spectrum is its geography: hundreds of flat-topped hills dot the terrain, providing natural barriers of earth to screen out radio noise from less quiet regions. The shape of the hills is important, as radio waves will normally diffract around or over a hill, but the flat tops inhibit this behaviour, making for a very effective screen against radio frequency interference.
Next up, on the topic of Interesting Technical Aspects of the SKA was Doctor Jasper Horrel, the general manager of science processing and inovation of SKA South Africabegan delivering a crash course on how the SKA (and radio telescopes in general) work. He began by pointing out that a radio telescope is really just a very sensitive and directional antenna, no different in principle from that on a car radio. It converts electromagnetic radiation of specific wavelengths to an electrical signal, which can then be converted into a form that human beings can understand. One particular wavelength which turns out to be very useful is that which is emitted by neutral hydrogen, as it is found in almost everything of interest to astronomers. By analysing the signal, and measuring the doppler shift from the true frequency, we can measure the relative velocity of an object towards or away from us.
The third speaker of the day was Maciej Soltynski, a consulting technology futurist, who spoke on Galaxy Clusters. But before geting to the main point, he first discussed how technology has changed the amateur astronomy landscape in the past few decades. Although professional astronomers have observing facilities that are rapidly making amateur observations less and less relevant, the Internet makes it possible for amateurs to access professional datasets and do their own work, using professional tools, writing papers that will be visible to professional astronomers. And all this can be based on the solid educational foundation of free university courses offered by prestigious universities.
After Maciej was done, Dale Liebenberg took the podium to discuss Astrophotography from a Backyard Observatory.
The last speaker before lunch was Auke Slotegraf, and his topic was Some Open Clusters I Didn’t Discover. The title was inspired by his recent discovery that certain well-known star atlases and charts have begun identifying small asterisms and potential open clusters with his name. He explained that this began when he began noticing these objects and drew up a catalogue of them. He numbered the objects in the order that he found them, and since it was the first list to include these objects, he has been given naming credit by some publishers. However he has decided to come clean and admit that in fact he was not the discovered of these objects – many were discovered by pioneering mappers of the Southern skies like Herschell and La Caille. If one browses through their observing notes, they frequently note seeing a neat little grouping of faint stars. Siince they never took these discoveries an further, however, Auke took the time to find them and catalolgue them. The atlas publishers were blissfully unaware that Auke was not in fact the first person to find them. Having cleared his conscience on this matter, he spoke a bit about the nature of open clusters, and what they can teach us about the rest of the Universe. In astronomical terms, open clusters are quite small, young, and dynamic objects, which makes them easy to age, and this in term gives quite precise measurements of the ages of their individual stars. But this also makes them hard to identify – after all, how do you tell the difference between a genuine cluster of young stars which will soon dissipate, and a chance grouping of stars that aren’t actually related at all?
After lunch, Willie Koorts presented A Pictorial History of SAAO Sutherland. He began by explaining that earlier versions of his presentation had over a hundred slides, and he typically presented it in under 15 minutes. As it happened, he kept the history flowing so fast and flashed so many images that I didn’t manage to take any notes at all for fear that I might miss something. Fortunately, I’m able to share the video to the right!
The next speaker after Willie was Doctor Barbara Cunow, who spoke on Doing Astrohotography with a DSLR on a Tripod. Doctor Cunow taught at the University of South Africa until a few years ago, as Associate Professor in the astronomy department. Unusually for a professional astronomer, she has always been very active in traditionally amateur activities, such as backyard astrophotography and sketching her view at the eyepiece with pencil and paper. By contrast with Dale Liebenberg, her photography is done under far from ideal conditions, using nothing more than a DSLR camera on a tripod in a heavily light-polluted suburban back yard. She mainly photographs star fields and deek-sky objects, by fixing the camera on its tripod and taking a series of short-exposure images without making any attempt to track. The gradual movement of the sky means that each image is slightly offset from the others in the set, and this provides automatic dithering for post-processing. She then stacks the images using a free image processing package called Regim. She then opens the combined image in photoshop, to subtract the sky glow. To do this, she first blurs the image, using the median function set at a suitably broad radius, and ends up with a map of the sky glow. This map is then smoothed using the gaussian blur function, and subtracted from the original image. The results, while perhaps not as impressive as those produced by more sophisticated techniques, are quite amazing. In this way, she is able to detect and image objects as faint as 9th magnitude, under conditions where the naked eye is usualy restricted to worse than 4th magnitude!
Continuing in the amateur vein was Johan Swanepoel, a retired electrical engineer who has recently impressed the local ATM community with his ambitious mirror making projects. He spoke about his most recent award-winning effort, The Shaping and Testing of Two 20″ Optical Telescope Mirrors. Johan exhibited one of a pair of 20″ telescopes he built at ScopeX 2010, and won an award for the attention to detail and meticulous design that follows naturally from his years of engineering experience.
I, Allen Versfeld, was the next speaker, with a hastily cobbled together presentation on Astronomy Online. A series of technical mishaps left me unable to access all my prepared materials, and so had to cobble together a replacement talk on a borrowed computer the evening before. Nevertheless, there must have been some interest in the topic as the talk seemed to go down quite well and attracted several questions both at the end of the talk, and later during coffee breaks.
I was followed by Neville Young, a recent acquaintance who comes from the same city as me, discussing his Lessons Learned in Outreach. Neville has been actively involved in outreach for 25 years with the Pretoria centre of the Astronomical Society of South Africa and has developed a number of simple teaching aids to demonstrate various aspects of astronomy. He sells these under his Starwaders brand, and they are surprisingly simple, original and effective. He recently published a book, which is selling extremely well across the country (If you’d like a copy, buy it through my Kalahari.net affiliate link here!).
Neville was followed by Pat van Heerden of the University of the Free State and of Boyden Observatory, talking about ASSA’s Contribution to Bloemfontein’s Two Observatories Project. This project was launched by the university’s Physics Department to preserve and restore the historic Boyden and Lamont Hussey observatories in Bloemfontein.
Keith Gottschalk spoke next, after the tea break, on the topic of Astronaissance: Communicating Astronomy and Space to the African Imagination. Keith was one of the more unusual speakers in that he thinks about astronomy from a socio-political position. He is a faculty member at the University of the Western Cape’s department of Policital Studies, a published poet, and was a political prisoner under the Apartheid regime. Keith conceived the concept of Astronaissance as a combination of an African renaissance, revival of African astronomy, and rise of space science and astronautics on the African continent.
He introduced his topic with a brief discussion of archaelogical evidence of ancient astronomy throughout Africa, and quickly moved through history to see how things have changed and how the focus moved towards european work. He discussed how the interest in science and astronomy in South Africa have blossomed since the fall of Apartheid, suggesting that the old government mindset did not encourage curiosity amongst the citizenry, and didn’t trust academics. At that time, science facilities (including the observatory at Sutherland which used to admit public tour groups only once per year) and museums were quite inaccessible, but that situation has been totally reverse. Interestingly, this point was challenged by Willie Koorts (a previous speaker who has worked as a technician at Sutherland for some decades), arguing that the opening up of facilities has been in response to increased public demand, and not as a result of any policy changes.
Keith then pointed out that if science is to continue to grow and take hold in this country, we need to put in more effort to counter pseudoscience reporting and advertisements, and daily newspaper horoscopes. As an example of what can be done, he described how he wrote a letter of complaint to a local newspaper that they were including patently false information in the form of a horoscope, and received a personal reply from the editor to thank him for the constructive advice (something which had never before happened in many decades of writing letters to editors!)
He finished by mentioning the growing field of astronomy tourism, in which game lodges and other dark-sky holiday destinations are starting to employ astronomers to guide visitors through a bit of stargazing. He seemed especially impressed by the efforts of www.lookingupsa.com and www.overthemoontours.co.za. He recommends that to encourage more such activity, we should lobby for our government to pass dark sky protection laws like those already implemented in the Czech Republic.
John Menzies took the floor next, to speak about Extrasolar Planets. At the time of the symposium, more than 800 exoplanets had been confirmed (and thousands of candidates awaiting confirmation), using a variety of method. John talked us through just what makes an exoplanet and presented one popular (but still controversial) definition: it has a mass of less than 13 Jupiters (Much heavier than this and it becomes more brown dwarf than exoplanet), and is not free-floating but is in orbit around something much more massive. There are several different methods used to find exoplanets. Direct imaging is what might come to mind as the most obvious method, but is particularly difficult. One analogy which explains why it is so hard describes setting up a spotlight several kilometers away, and then trying to photograph a firefly perched on its rim. Nevertheless, this method has been used succesfully, if only a very few times. Exoplanets are more commonly found via dynamical methods, where close observations of a star reveal variations in its motion due to the gravitational pull of its planets. These variations can be measured by detecting tiny doppler shifts in its spectrum, or by very precise astrometric observations.
When photometric methods are used, astronomers look for either transits, when a star’s light is partially obscured by a transiting planet, resulting in a very slight dimming, or microlensing events when the background star field is very slightly distorted. This is caused by the planet’s mass causing a very small gravitational lensing effect.
The final method used to find exoplanets is timing: many objects in the sky exhibit some sort of regular behaviour, such as the flashing of a pulsar, or the orbits of a binary star. If there is one or more exoplanets in that system, it can effect the timing of the event in a predictable and measurable way.
John then talked about the likely nature of the exoplanets themselves, showing a plot of planetary mass against its radius. This is reminiscent of the famous Hertzprung-Russel diagram, in that it suggests strong constraints on the relationship between these two properties.
He then discussed two exoplanet surveys being conducted at Sutherland. First is the KELT telescope, taking regular photometric images of a very large (26° x 26°) area of the sky, looking for planetary transits. The competing project, SuperWASP South, uses a similar method. But the most successful project yet remains the Kepler infrared orbital telescope, which has discovered the bulk of confirmed exoplanets, and has recently been extended by another four years.
The last person to speak before the doors were opened to the general public, was Magda Streicher presenting a Collection of Pencil Sketches of Astronomers. Magda is a past president of ASSA, and has won awards for her consistent deep-sky observations. She has a regular column in the MNASSA in which she introduces a constellation and discusses the deep sky objects which can be found within it. Her latest book, Astronomy Delights, is a personal account of her observations of some of the most charming Southern Hemisphere deep-sky objects.
Magda recently commisioned a local artist to produce a series of pencil sketches of famous astronomers throughout history. She has collected these sketches, along with detailed biographies, in a volume which she presented to the current ASSA president, for inclusion on the society archives. Hopefully, the society will have the volume printed as a book, and made available to the general public. Her talk was a montage of the various images, which she accompanied by reading the associated biographies.