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Quiz Evening - December 21st |
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Plenty of snacks and beverages were provided by members. Tony Buick showed us the movie clips he'd not been able to show at the previous meeting. Then Jim Mehta and Tom Meechan presented us with the traditional Xmas quiz. This year the Moonstarers carried off the honours, though there were cries of "Foul!" when the Deep Sky round was cut in the interests of finishing before midnight. The musical round completely flummoxed the Moonies, who finished in last place, but their team leader won the evening's raffle, so not all was lost! |
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Members Evening - November 23rd |
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Gilbert Satterthwaite gave the first talk of the evening on "Airy's Altazimuth Telescope". This instrument was installed at Greenwich by Airy, and was used very successfully to record the Moon's position with greater accuracy than had previously been possible. Considerable attention had been given to its design and placement. It weighed about 2000 pounds, quite a substantial amount for a telescope of modest size, and this contributed to its success. Sadly it was replaced at the end of the 19th century by a larger but less well designed (and less successful) instrument, and Airy's telescope is now in storage in the Science Museum. There is some hope that it may be put back on display sometime.
Tony Buick then gave a short talk, somewhat frustrated by technology, about his recent attempts to capture images of man-made satellites.
Greg Smye-Rumsby brought the evening to a close with a short talk about "Planetary Occultations". These events are so rare that there are no recorded observations, but Greg put his artistic skills and astronomer's knowledge into constructing images of some of the possible events in the next few thousand years, ensuring that relative sizes, brightness and illumination of the planets was as accurate as possible. He also mentioned that the accuracy of any predictions is highly dependant on the correctness of the data from which they're derived and the accuracy of the calculations. However, as most of the events he listed were over a century in the future, acccuracte predictions are only of accademic interest to most of us. |
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Ghosts and Poltergeists - October 26th |
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Tony Sizer gave us a seasonal talk on "Ghosts and Poltergeists". The astronomical ghosts he mentioned mostly turned out to be optical effects mis-interpreted by the observers who "discovered" them. They included the non-existant large moons of Venus and Mars, which were eventually explained, quite literally, as gleams in the observer's eye, multiple reflections off the observer's cornea and the eyepiece he was using. A few of the ghosts did turn out to be genuine astronomical objects mis-interpreted by the observers concerned; perhaps the most remarkable being the planet Uranus being mistaken for a moon of Venus. Astronomical poltergeists have been rather more numerous. The best known is probably the planet Neptune, which was discovered because of the effects it had on the orbit of Uranus. Mathematical calculations led to a predicted location, and the new planet was discovered very near its predicted position. Subsequent attempts to extrapolate the process to discover a large planet orbiting beyond Neptune led to the discovery of Pluto, but the discovery owed a great deal more to the careful systematic work of its discoverer than to the mathematical predictions. Similar predictions also suggested that there should be a planet orbiting inside the orbit of Mercury. So certain were some that this planet existed that they even named it Vulcan. However, the mathematics used to predict Vulcan's existance was eventually shown to be inadequate, and when it was corrected Vulcan vanished. Many other moons and asteroids have since been discoveerd by making predictions mathematically, and at least a few have been shown subsequently to have been pure chance. It was a fascinating evening's talk, and by way of icing, members were able to use the Society's new Meade Light Bridge telescope to view comet SWAN. |
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Journeying into the Unknown - September 28th |
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Glyn Collinson of the Mullard Space Science Laboratory gave us an interesting and well-received talk titled "Solar Orbiter - Journeying into the Unknown" about the work being done for the Solar Orbiter. |
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Deep Sky Imaging - August 24th |
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At this evening's Members Evening, Mike McRoberts and Chris Suddell gave us an illustrated talk on the business of "Deep Sky Imaging". First Mike, who'd brought his portable kit along, talked us through its component parts in a usefully non-technical manner. Then Chris took us through the process of capturing and processing images. He talked about dark frames, hot spots, flat fields, narrowband filters, and quite a bit else besides. Along the way he gave demonstrations of the processing that can be done using AIP4WIN and Photoshop. He ended the evening in traditional fashion by showing us a selection of images he'd prepared earlier. |
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Roger O'Brien's talk on "Cosmology" was a conversational journey from the Steady State Theory to the Big Bang Theory, with reference to the discovery of the Cosmic Background Radiation, and a practical demonstration of the kinds of measurements needed to demonstrate that the Universe is expanding. Along the way he stressed the importance of testing scientific theories by using them to make predictions and then comparing observed results with those tredictions. The Cosmic Background was a good example. Both the Big Bang and Steady State theories could explain it, but the nature of the actual observations are much closer to the Big Bang theory's predictions than the Steady State theory's ones. |
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Jack Martin made use of slides, laser pointers, and diffraction gratings to illustrate his talk on "Spectroscopy". By shining both a green and a red laser pointer through the same grating he demonstrated the spectral spreading a grating produces, and how different gratings spread the spectrum to a greater or lesser degree. The grating he uses has 200 lines per millimetre, and puts three-quarters of the light falling on it into the first-order spectrum. He uses it to produce spectra of stars on photographic film at the prime focus of his Dobsonian telescope. By allowing the star to trail in a direction perpendicular to the axis of the grating's dispersion, a clear spread spectrum can be captured on film using exposures of between 15 and 30 seconds. He favoured Ilford Delta 400 ASA as it was sufficiently red-sensitive to capture spectral detail around the Hydrogen-alpha line. He showed some spectra captured on other emulsions with different sensitivities, and some of the spectra were very obviously incomplete. He showed us spectra of various types of star from white-hot Mintaka to dull red Betelgeuse, the blended spectra of various double stars, and the emission spectrum of Gamma Cassiopeiae. There was some discussion on the possibility of using CCD imaging, but Jack clearly still favours film. |
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Observing the Sun - May 25th |
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John Chapman-Smith, a member of the council of the Society for Popular Astronomy, and a past director of its Solar Section, gave us a talk on the practical aspects of "Observing the Sun". No talk on this subject would be complete without serious warnings about the dangers involved. He stressed the importance of using projection to observe the Sun indirectly, and of taking precautions like capping or removing finder scopes, reducing telescope aperatures, and not using telescopes with any flammable components in them. Even looking directly at the Sun with the un-aided eye will cause damage. Anything which concentrates the infra-red heat radiation can be very dangerous. Some of his slides showed the damage sustained by filters and eyepieces. Eyes are much more easily damaged.
Having covered the safety aspects thoroughly, he then went on to describe the kinds of features that can be observed, and how they should be recorded. He then explained how more experienced observers might use various safe filters to photograph and observe the Sun, and added more cautionary tales about some of the un-safe filters that should never be used. He ended his talk by showing us some images taken using Hydrogen Alpha and Calcium K filters. These allow observers to see more features, including filaments and prominences, but they are still quite expensive. Even though they do filter out the harmful radiation when used properly, observations must still be carried out taking all appropriate precautions. |
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Landing on a Comet - April 27th |
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Simeon Barber, who gave tonight's talk entitled "Landing on a Comet", stood in at short notice for Andrew Ball, who was called away to a meeting abroad. His presentation, though, gave no indication of this. During the evening, he outlined the results of past spacecraft mission to comets and gave details of the ROSETTA mission recently launched to rendezvous with comet 67P/Churyumov-Gerasimenko. He also showed some of the experimental apparatus which he and his team have developed for this mission. This equipment is a remarkable example of miniaturisation, a mass spectrometer which usually occupies a bench being reduced to the size of a coffee cup. The total mass of the equipment on the spacecraft is very strictly limited: hence the need to keep everything as small as possible. A fascinating evening: we hope to invite Simeon back again some time. However, as he became the father of twins a few days after the meeting, he may not have as much spare time in the future! |
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Film vs. Digital - March 23rd |
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Our second meeting at the Bonus Pastor School in Downham co-incided with a parents evening, so we met in a classroom upstairs rather than in the main hall. Our speaker was Robin Scagell, and he gave us a very clear and informative talk on the relative merits and disadvantages of film and digital image capture as applied to astronomy. He concluded that digital imaging usually has an edge but that there are still advantages offered by film, especially where the subjects are constellations and star-trails. |
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The High Elms Nature Centre was closed just before our Annual General Meeting. An alternative meeting place at the Bonus Pastor School in Downham was arranged at short notice, and the meeting was very well attended. Paul Whitmarsh gave us a review of the Society's year before the main business of the AGM. Ray Hemming, who has been our Treasurer for twenty years, was presented with an honorary membership by our President Gilbert Satterthwaite. After the coffee (and tea) break we heard two short talks. The first, by Tony Buick, was about a possible TLP (Transient Lunar Phenomenon) he noticed on one of his many photographs of the Moon. The second was a twenty minute journey through the life of the universe by Greg Smye-Rumsby. |
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Astronomical Treasures - January 26th |
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Our speaker this evening was Kevin Johnson from the Science Museum, who gave us a talk about Astronomical Treasures. The museum has a collection of over a quarter of a million objects, and more than 180000 of them are in storage. The collection includes many objects of interest to astronomers, including the pair of globes once owned by George III, the celestial globe which used drawings of the maker's other products to illustrate appropriate constellations, and Dickert's Lunar hemisphere, which is over 4 metres in diameter, and has many hundreds of craters mapped in relief. Instruments in the collection include ones used by Smyth, Lee, the Herschels, South, Groombridge, Lord Rosse, and many others. Some were used to make important early observations, and all had fascinating stories to tell. |
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