Aina Musaeva is an astronomy guide at Sydney Observatory while an honours astronomy student with The University of Sydney.  She is a keen observer and member of the Sydney City Skywatchers, regularly presenting at meetings.  In 2011 Aina received a summer studentship from the Australian Astronomical Observatory  (AGUSS) for a ten week program at the Gemini South Telescope in Chile. Here is her report.

My project:
I was working with Tom Hayward and Fredrik Rantakyro characterising the image quality of the Gemini South 8-meter telescope. We wanted to know which parameters affect the image quality and how we can better plan the queue when observing the science targets with the telescope. To do this we analysed the Gemini Engineering Archive data, which contains information from various environmental, instrumental and telescope sensors. So I wrote some data processing and analytical routines in the programming language Python which I had to learn for this project. Among other things we discovered that seeing (one of the most important image quality factors for the telescope targets in the optical wavelengths) was worth when pointing the telescope to the south. Such discoveries can be utilised when optimising the use of the telescope. Imagine you are a scientist and you applied for the telescope time to take images of some galaxy currently located in the southern part on the sky. However for your particular object you require very high image quality. Then the queue scheduler of the Observatory will make sure that you get your time on the telescope when this galaxy is as far from south as possible because even though the science instruments are capable of producing the images of the quality you required the environment of the site will degrade the quality.

Gemini South Telescope © by Thomas Matheson

Gemini Observatory:
Gemini has its own compound (recinto) where many astronomers reside. The compound is guarded 24/7 so very soon we knew most guards by names and they knew us. The offices are located at the same place so it is an easy 5 minutes walk from home to work. We lived in one of these houses together with Joe Callingham, the other recipient of the AGUSS. We also had our own office where we worked for 10 weeks. The Observatory’s staff has made us very welcome from day 1. We were introduced to ALL the members of staff, how often does that happen at the places people work these days? Apart from working on our own projects we also went to various colloquia which are organised every week, sometimes even several times a week. It has been very interesting to hear what people are doing across the world with the data collected with Gemini and also other telescopes. It was also a surprise for us to discover that about 80% of staff are engineers and not scientists. In the university environment it is quite the opposite, however it is understandable as the Observatory provides the service to the community and its most important objective is to deliver that service. Therefore a lot of effort is put into optimisation of the telescope performance.

Looking into the spectacular eight metre mirror! Photograph Aina Musaeva

The telescope:
We were lucky enough to go up to the telescope twice. The first time during the laser commissioning run, which was especially exciting for Joe as his project was all about that laser and the sodium layer it interacts with. The laser is absolutely impressive, 50W laser requires airplane spotters so the laser doesn’t interfere with their operation. So the first time we had a large team of people even though there have been no science targets observed that night. The mountain the telescope was on is about 2715 m high and is called Cerro Pachon. The primary mirror of the telescope is 8 meters in diameter and is absolutely majestic. So if the altitude hasn’t quite taken our breath away, the sight of the mirror has surely done the job.

8 Meter Mirror
On the same mountain there is also another telescope SOAR with a “humble” 4 meter mirror. The telescope is completely computerised, however when something goes wrong there is an allowance to deal with issues manually. The dome opens up a few hours before the sunset so the air temperatures outside and inside the dome come into equilibrium by the time the observations are due to start. This is important since one of the annoying things in terms of astronomical seeing is thermal currents forming inside of the dome that degrade the image quality. The second time we were on the mountain during the new moon and we could observe so many celestial objects! I brought my binoculars with me but the sight is so dark, you can just observe with your own eyes Gemini Observatory has a hotel for the astronomers who are working at the mountain which is only 5 minutes away, so after a long night they don’t have to travel long before hitting the pillow.
We were also lucky to visit Las Campanas Observatory which has a whole bunch of telescopes! The seeing at that site is absolutely exceptional!

La Serena:
The base facility of Gemini is located in a beautiful town called La Serena. It is not very big but has a nice climate: it never gets too hot or cold, unless you move into the desert. However it never rains here, we were surprised of how generous people were watering their gardens provided the fact the dam level was only 30%. La Serena has a lovely beach which stretches as far as the eye can see. The water however is quite cold even though we were there in the heat of summer. People are laid back, nobody seems to rush anywhere unless it is of course on the road: drivers in Chile are crazy and impatient. I even asked one of the astronomers why is it that so and they told me that if you are planning to spend a solid hour for lunch in some nice cafe, you have to hurry getting there!
What impressed us most in La Serena was actually its fruit and vegetable markets! Imagine the freshest fruit you have ever tasted – but this is better! And incredibly cheap! I swear you could go to the market with $20 and buy the whole market! Apart from grapes, watermelons, apples and other common fruit they also have these interesting local fruit that are even hard to describe, you just have to try those for yourself! A lot of those fruit flavours are added to ice-cream, in La Serena they love their ice-cream, it is sold absolutely everywhere! I also loved that they had so many berries, including those that you never ever see in Australia but those that I am used to in Russia: like raspberries and red current.

Apart from the fruit markets La Serena also has lovely craft markets where you can get gorgeous knitted items with South American themes and jewellery. In Chile they love using the stone called Lapis lazuli in jewellery, it is very unusual but beautiful so I sure brought some home with me.
There are no high buildings in La Serena so at night the whole harbour with all its beautiful lights is like on your palm, especially viewed from where we lived (up on a high hill).  Right next to La Serena there is a port town called Coquimbo with a huge Millennium Cross and a fish market.

Mote con huesillos. Photograph Aina Musaeva

Food and drink:
Many cafes have this lunch specials where you can get 3 course lunch for as little as $6! There are many different Chilean dishes we have tried among which are: pastel de choclo (baked corn paste with meat), completes (hot dogs with avocado) and ceviche ( fresh fish in lemon juice). One of the common sweet drinks is mote con huesillos, which is a sweet water with barley and pickled peaches. I know it doesn’t sound appetising but it was most delicious! Pisco is some kind of fortified wine that is popular but in my opinion their best alcoholic drink is actually red wine and in particular wine made of the carmenere grape which disappeared from European vineyards a long time ago.

I visited Old Perth Observatory, located in King’s Park on Mt Eliza, a fabulous site with park and river views, in November 2011. The site is under the custodianship of the National Trust of Western Australia and the purpose of my visit was to see what remained of the Old Perth Observatory and look for evidence of the Astrographic Catalogue work as part of broader doctoral research for The University of Sydney Museum Studies Department.  I was treated to a behind the scenes and up the tower view by the CEO of the National Trust WA, Tom Perrigo, and the heritage officer, Dan Kloszer Skjold.

Fig 1: Toner Stevenson on top of the Tower of Old Perth Observatory Nov 2011

There is a fabulous 1896 image of the day the foundation stone for Perth Observatory was laid showing vigorous celebration and how important this scientific endeavour was to the colony. Even though Perth Observatory was completed in 1900, well after Sydney Observatory (1858), there are parallel histories.  Both were significant for establishing and maintaining order through carefully determining and communicating the time, both had important roles in land surveying, including determining State borders, in the early days of the colony. Like Sydney, Perth Observatory also had a period when buildings and instruments were removed from the site with the Astrographic dome demolished and relocated. This occurred in Perth in 1965 and in Sydney from 1982. The Government Astronomer’s residence and offices was one of three buildings on the site, it is the only one remaining.  This building provided luxurious accommodation for the astronomer and his family.  It has a curved balcony with sweeping views on the first floor, five bedrooms, two boudoirs, and a dressing room.  On the ground floor are several lobbies, a substantial kitchen and laundry, and separate toilets for the workers, servants and children. In the official work area, which is considerably smaller than the residence, there is an impressive room with bay windows for the Government astronomer’s office (Fig 6), a library and an office for the astronomers and where the computers, then humans, and clerk sat.  There is no evidence of telescopes in this building.

The first Director and Government astronomer was William Ernest Cooke, who was appointed by the first premier of Western Australia, Sir John Forrest in 1896.  Cooke energetically sought to meet the demands of the colonists who wanted to know things like the time and the weather.

Fig 2: This photograph taken around 1898 shows the three main buildings: the Transit Observatory (far left), the Astrographic building and dome (centre) and the administration office and house is the larger building. State Library of Western Australia 011494D.

To provide accurate time required setting up an observatory with a Transit telescope, and taking the advice offered by Cape Town astronomer David Gill for a shaded but airy structure, Cooke designed a Transit house that was a protective cover for the telescope very well suited to the Perth climate (Fig 2). The Transit telescope was installed in 1898 and an ingenious contraption was assembled to fire a small cannon signalling one o’clock to the growing city (Fig 3).  As reported in a previous blog post, there was also an electric signal sent to Fremantle Harbour so that the timeball, could be dropped there simultaneously, The one o’clock gun was replaced by a foghorn and then ceased altogether in the 1950s when the Observatory sent accurate time to the radio stations.

Fig 3: Firing the One O’Clock gun, a drawing in the State Library of Western Australia Collection.

Perth Observatory photographed a large section of the sky for the international project called the Astrographic Catalogue. Cooke had an Astrographic building constructed and purchased a Howard Grubb telescope with a photographic lens as specified for the Carte du Ciel and Astrographic Catalogue, so Perth was well prepared in 1900 when the Western Australian government agreed to take over the zone originally assigned to Rio de Janeiro. By January 1901 Cooke was ready to start photographing the stars and he regularly corresponded with H.C. Russell at Sydney Observatory. Russell had been involved in the Astrographic Catalogue from its very beginning in 1887.  Between 1908 and 1921 twenty four volumes of the Perth Catalogue were published by W.E. Cooke and H.B. Curlewis, with the last three catalogues published during H.S. Spigl’s directorship when the remaining glass plates, sent some years prior to Edinburgh for measuring, arrived back in Perth in 1953 (Utting, vol1:41). There is a wonderful image in the Powerhouse Museum collection showing the inside of Perth Astrographic dome and the Astrographic telescope .  The Astrographic telescope is now installed and operational at Perth Observatory Bickley where the original dome was placed on top of a new building.

Fig 4: Perth Observatory, photograph taken around 1901. Notice the instruments on top of the tower, and astrographic building courtesy Perth Observatory Collection.

Cooke called the tower on top of the main building the ‘anemometer tower’ (Utting, vol 1:97). While meteorology records for Perth date back to 1829, it was in 1898 that the anemometer (an instrument for measuring wind speed) was installed on top of the Perth Observatory tower.  Cooke established an extensive network of weather stations across WA. Recording and reporting the weather became the most publicly recognised activity on the site, although it was not under direct control of the astronomer after the Federal Bureau of Meteorology was established. However, for a considerable time the brothers Curlewis were in charge of both the Observatory and the state Bureau of Meteorology. In the 1980s the National Trust became custodians and the building, by then in very poor condition, was restored and re-opened in 1988.  An anemometer, that still looks very like the original one seen in old photographs, is stored in the tower.

Fig 5: Old Perth Observatory today. Note the generous balcony and tower. The Dumas building, left, was constructed after 1965 once the meteorology lawn, Transit building and Astrograph building were demolished. Photo T. Stevenson.

Timekeeping, meteorology, seismology, surveying and astronomy meant that the observatory and its scientific staff and equipment were all important to the governance of the colony.  This changed dramatically over the following century due to the Federation of science, a depression, two World Wars and the changes in state and federal government responsibilities.  Nonetheless this site still holds a remarkable history and one the National Trust is planning to make more public. There is a more detailed Perth Observatory history written by Wayne Moredoundt for the Heritage Council.

Fig 6: Once the Government astronomer's office, now the National Trust boardroom. Photo: T. Stevenson

A particularly exciting aspect of astronomy is ‘discovery’. Sitting in front of a computer, looking at telescopic data, you suddenly realise you are the first person ever to have witnessed some astronomical event. But frustratingly there is often noone else around to share your discovery with!

The bright star in the centre of the right-hand image exploded to become SN1987A, clearly visible in the left-hand image. Copyright Australian Astronomical Observatory, photo by David Malin.

Ian Shelton must have felt that surge of excitement 25-years ago on February 24 1987, when developing photographic plates of the southern sky. One, of a region near the Large Magellanic Cloud, showed a bright star where no bright star should be. Stepping outside he looked up and became the first person in almost 400 years to see a supernova with his unaided eye.

A supernova is the death of a massive star, one that begins life with more than about eight times the mass of the Sun. For most of their lives stars exist in a delicate balance with their enormous mass trying to collapse in upon itself while light (or radiation ‘pressure’) pushes out to support the star. When the star’s fuel runs out it’s on a one-way trip to implosion.
The collapse happens inside-out, the central regions go first leaving the outer envelope unsupported. As the outer layers come crashing down a shock wave is generated which blows those outer layers right off the star. All we see, however, is a star which brightens suddenly then dims over several months, as if someone is playing with a dimmer switch.

But of course this supernova didn’t really occur in 1987. The star, Sanduleak -69º 202, was actually in the Large Magellanic Cloud and that is about 160,000 light-years away. What Ian saw was just the delayed ‘movie’ of an explosion that really happened 160,000 years ago. That movie of the exploding star is still travelling, at the speed of light, through our galaxy. It passed by Earth in 1987 and recently passed the bright star Vega. In a year or so it is due to reach the northern star Chi Draconis, in the northern constellation, the Dragon. Chi Draconis is on the opposite side of the celestial sphere to SN1987A.

A classic image of SN1987A taken with the Hubble Space Telescope in 1994. The rings are gas shed from the progenitor star and then illuminated by that star's explosion. Credit: Dr. Christopher Burrows, ESA/STScI and NASA.

SN1987A taught us a lot about exploding stars. We used to think only red supergiant stars (like Betelgeuse in Orion) could go supernova, but this one was a blue star; the detection of neutrinos two hours before the visible light that Ian saw helped us understand what really powers the explosion; and such a bright supernova in an age of radio-telescopes, digital cameras and spacecraft has provided a wealth of information that still keeps astronomers busy.

One significant change between 1987 and now is hidden in the name: SN1987A. The ‘A’ means it was the first supernova discovered that year, in a time of photographic film and eyes at telescopes. In 2012 (up to Feb 23) already 33 have been reported – many of these found by automated telescopes with digital cameras for eyes and a computer algorithm making the discovery.

I am new to Sydney Observatory, as I only started interning in the beginning of January.  I hail from Chicago,Illinois right in the middle of Midwest America. Directly west of Chicago is the Mississippi River, on which sits my university, Augustana College (Augie).  I’m here studying/working abroad in Sydney, and frankly, I am loving life.  Right now, normally I would be in the middle of winter, walking to class through snow in -20° Celsius (-5° Fahrenheit in my terms) weather with biting winds.  Needless to say, I much prefer the (somewhat) sunny Australian summer weather this time of year.

For my internship in Sydney, I was lucky enough to be placed at Sydney Observatory for seven weeks to gain work experience in event management.  Bonus: it’s an observatory and everyone working here is obsessed (in only the best way possible) with astronomy.  And frankly, I think it’s awesome. I haven’t taken a science class, let alone one that covered astronomy, since year nine.  My knowledge of astronomy stops at the Sun, the Moon, and the (now) eight planets in our solar system (I’m still having a hard getting over the fact that Pluto was bumped down from planet status).  But I have learned so many little tidbits from joining on the tours or just chatting with the staff during work. 

Everyone is so passionate about astronomy here, it’s hard not to be interested. And since I wasn’t even trying to resist, I have learned some very fascinating information which I am keen to share with my fellow classmates (there are 48 of us from Augie running around Sydney).

The Southern Cross and Pointers as photographed by Sydney Observatory's Geoff Wyatt

Such as last week when I was riding a ferry from Darling Harbour back to Circular Quay and could quite easily identify the Southern Cross and the two pointer stars by it (sorry if they have proper names, but I am still new at this) and proceeded to announce this to all my friends.  Also, I knew that if I drew a line to where they would intersect and dropped straight down to the horizon, that point would be directly south.  The fact was, I was able to see that as easily as if it was the Big Dipper, a constellation I have been staring at my whole life back up in the Northern hemisphere.

 Also, I finally managed to check out a night time tour, and can I just say, I am thrilled that the clouds didn’t scare me away.  My roommate and I were a little wary of the weather, but we decided to take a chance anyway, and it paid off.  We started out the evening in the Planetarium learning about Aboriginal tales of the constellations, and by the time we finished that segment, the sky had cleared! NO CLOUDS! We quickly headed up the North dome and through a telescope we learned is quite a treasure, we viewed Jupiter and three of its four Galilean moons followed by the Orion Nebula (my personal favourite).

One little thing that kind of blew my mind was that while we were taking turns looking through the telescope at the Orion Nebula, the guide had to keep readjusting the telescopes position (just a miniscule amount).  This was because Earth was moving and we had to account for that in our view. By looking through that telescope about 1,500 light years away, I could actually observe that the Earth moving, that I was moving. It was one of those moments that reminds you there is so much more beyond Earth’s atmosphere, something I think we non-astronomers tend to forget.

Emily in the South Dome of Sydney Observatory looking through the 1874 telescope by Schroeder

Like most museums the Powerhouse collection is larger than we could possibly display. The Powerhouse Discovery Centre (PDC) at Castle Hill contains shelves full of historical ‘treasure’ – and this includes clocks & telescopes once used at Sydney Observatory.

On Saturday February 11, the PDC holds its first Open Day for the year and I will be conducting a ‘Behind the Scenes’ tour of H-store to show off some of our most significant clocks and telescopes. Highlights will include Governor Brisbane’s Hardy ‘regulator’ clock of 1808,  George the Speaking Clock and the ultra-precise Rubidium atomic clock that disseminated time from the Observatory until the 1980s. Telescopes include the 13-inch Melbourne astrograph used to make the first photographic map of the sky and the long-lost “horseshoe” style telescope mount, invented by our very own Henry Russell in 1878 and now used for Australia’s largest telescope – the Anglo-Australian Telescope.

There are many other activities to get involved in for young and old: A Chinese Water Dragon, ‘Rocket Science’ and the Peppin Merino amongst others. Find out all the details and how to book on the Open Day flyer.

Please note this event is NOT being held at Sydney Observatory and, while the day is open to all,  you must be 12+ years old to join my ‘Time & Telescopes’ tour.

Toner Stevenson, Manager Sydney Observatory, reports from Western Australia.

My recent visit to Perth included visiting the Observatory at Bickley. Not only was I treated to a fabulous lunch prepared by and shared with all the observatory staff, there was the opportunity to go behind the scenes with acting Director, Ralph Martin, astronomer Dr. Andrew Williams and education manager Greg Lowe.

Perth Observatory, the 1896 foundation stone is on the lower right side. Photo T. Stevenson, 2011

On approach up the long driveway that separates Perth Observatory from Bickley’s suburban sprawl the first thing I noticed was the foundation stone dated 1896 in front of a clearly 1960s modernist building. This stone, laid by John Forrest, marks the first Perth Observatory building established in Kings Park, close to what is now the city.  Like Sydney Observatory during the late 1800s, the observatory was the colonial centre for astronomy, timekeeping, meteorology and surveying, covering the vast state of WA.  Over time these functions were mostly removed or reduced significantly, and in 1965 Perth Observatory was relocated to the suburb of Bickley, about 40 minutes outside Perth.  Fortunately more than the original foundation stone was relocated from the city site as I soon discovered.  Many significant items of a past era shared with Sydney Observatory have been carefully kept and some were still in use.  From the minute I stepped through the door I sensed the strong ties between Perth and Sydney Observatories re-connecting, it felt like catching up with a dear friend. 

William Earnest Cooke (seated left) Director of Perth Observatory, pictured with Yeates, Curlewis, Ackland and Jocelyne in front of Old Perth Observatory, 1901. Courtesy Perth Observatory Collection.

The astronomer and meteorologist William Earnest Cooke was the first Western Australian Government astronomer (1896 to 1912) and in 1912 he accepted the Directorship of Sydney Observatory.  It was through Cooke’s initiatives that in 1900 Perth Observatory undertook work on the Astrographic Catalogue and Carte du Ciel.  Both Sydney and Melbourne observatories had already begun work on this ambitious international project to catalogue and chart the entire sky. Like Sydney, Perth Observatory has an active public day and night tour program , publishes an annual astronomy almanac and supports its heritage work through an adopt a star program, drawing on its own catalogue of stars also providing recipients the opportunity to view their star. 

Perth’s astrographic telescope by renowned Irish instrument maker Howard Grubb is in impressive working order and Greg Lowe showed me how this is demonstrated as part of the regular night tour.  Designed to photograph the stars, this telescope was the standard chosen for use by the British Observatories participating in the Astrographic Catalogue.  Sydney Observatory’s ‘star camera’, a unique telescope design by Henry Chamberlain Russell, had only the lens supplied by Grubb. But the Melbourne Astrographic telescope, moved to Sydney Observatory in 1948, appears almost identical to the one in Perth. These instruments are in the Castle-Hill store pending conservation. The original Perth Astrographic dome was removed from the 1896 building and relocated to Bickley. It is one of a number of telescope domes, some of which are made accessible to the public. This restored 1910 Calver (Newtonian) telescope can be compared to the view through the contemporary 40cm MEADE Schmidt Cassegrain.

Acting Director, Ralph Martin with the 1910 Calver (Newtonian) telescope used during night tours. Photo T. Stevenson, 2011

This site is a living astronomy archive with a comprehensive astronomy library, extensive glass plate negative collection, heritage instruments and a complete set of Astrographic Catalogues.  An exhibition displays some of the treasures from their collection and is well worth a visit. At night you can experience the night sky from a relatively dark sky environment through telescopes. 

Perth Observatory is the only State-run Observatory still equipped and staffed for research and as such the public are also able to witness science in action.  High up on a 15metre tower is the primary research telescope and largest dome on the site. The Perth-Lowell automated telescope is operated remotely and has a sensor that closes the dome in wet weather. Ralph Martin spoke about the partnerships Perth Observatory has formed with Universities, major projects such as ICRAR (International Centre for Radio Astronomy Research)  and Perth Observatory’s gravitational micro-lensing work which has led to the discovery of smaller planets rotating around distant stars. You can take a virtual tour of the Perth-Lowell observatory without climbing all the stairs.  

Astronomer Dr. Andrew Williams with the Perth-Lowell telescope. Photo T. Stevenson.

I also visited the Old Perth Observatory, a grand residence for the Government Astronomer. With 2012 the centenary of W.E. Cooke’s departure from Perth to the Directorship of Sydney Observatory expect other blogs to follow throughout the year.

The ROSAT X-ray space telescope is due to re-enter Earth’s atmosphere over the coming weekend (22-23 October, 2011). Dr Martin Anderson, Astronomy Educator at Sydney Observatory, writes about his experience using ROSAT.

I was fortunate enough to be part of a space mission aimed at investigating our universe using X-rays. To do this I used a German  satellite named ROSAT. ROSAT or Röntgen satellite was named in honour of Wilhelm Röntgen, the scientist who discovered X-rays. Actually, Röntgen was awarded the first Nobel prize in Physics in 1901  for discovering X-rays.  To see X-rays you need to be in space as Earth’s atmosphere stops X-rays from reaching the ground. Once launched in 1990 ROSAT was free to observe the X-rays coming from stars and galaxies as it orbited the Earth.

 

If you’re wondering how the X-ray sky compares to what you see with your eyes then look at the two images below. The first image show how the “Saucepan” in Orion appears in visible light and in X-rays. The second image shows an image captured by ROSAT of the Moon, caused by X-rays from the Sun reflecting off the Moon’s surface.

ROSAT X-ray image and optical telescope image showing the “Saucepan” in the constellation of Orion. Credit: Max-Planck-Institut für extraterrestrische Physik.

 

ROSAT X-ray image of the Moon caused by X-rays from the Sun reflecting off the Moons surface (29 July 1990). Credit: Max-Planck-Institut für extraterrestrische Physik

 

 

Created using Stellarium 0.11.0

On a dark clear night who hasn’t looked up to see the last hint of meteor fading from sight? “Damn it why couldn’t I have seen all of it?” And then perhaps minutes, hours or nights later you do get to see one while everyone else is looking the wrong way! Looking for meteors or “shooting stars” can be very frustrating.

Every now and then however the probability of seeing some increases as the Earth silently glides through the dust trail left behind by a comet. This causes a meteor shower.

Next month is one of the better chances or is it? The Orionid meteor shower this year should start around October 2nd and go through to November 11th but the peak is from October 19th to the 22nd.

The Orionids are the result of dust left behind by that most famous of comets, Halley that last swept by in 1986 and will return in 2061. As the Earth rotates on its axis while orbiting the Sun the relative velocity of up to 70km/s makes short work of the dust hitting the atmosphere between 80 and 120km up. The result is a short sharp streak of light in most cases though sometimes a more spectacular fiery event can be seen lasting for several seconds.

So what can we expect this year? A lot depends on the observer’s location. In a bright city or dark country side, clouds, fog and latitude. The closer to the horizon the key point known as the Radiant is the poorer the view and the number of visible meteors drops.

For the Orionids the Zenithal Hourly Rate (ZHR) and therefore maximum under PERFECT conditions is above 23 meteors per hour. For major locations like Sydney this drops but be how much?

The following formula helps.

Where HR is the hourly rate for an observer, r is the population index, in this case 2, which describes the numbers of fainter meteors of each magnitude, LM is the observer’s average limiting magnitude ie how bright the sky is. For cities like Sydney this would be about 4.5 until the time of Moonrise when the sky becomes much brighter. A is the altitude of the shower’s radiant above the horizon in degrees which sadly for the 22nd will only be about 17 degrees above the ENE horizon.

So for Sydney at around 2am on October 22nd (Moonrise is at 2:39am)

(HR) = 0.84 which is sadly well below the sporadic or background rate of 4.

This means this years Orionids are effectively a non-event for us on the East coast of Australia in 2011 as the radiant is so low before the rising waning Moon. Maybe we will have better luck next year!

(1) http://www.namnmeteors.org/

The stars of the constellation of Sagittarius the Archer. As indicated on the drawing, the constellation has an informal alternative name of the Teapot. The positions of the two best known nebulae in the constellation, Messier 8 and Messier 20, are also shown. Image and copyright Nick Lomb ©, all rights reserved with the drawing of the teapot from Microsoft clip art

In August/September the constellation of Sagittarius the Archer is almost overhead in the early evening as seen from Australia. It is one of the 13 constellations of the Zodiac, that is it is one of the 13 constellations in front of which the Sun moves during the year, and it is the constellation that follows Scorpius the Scorpion. It is normally drawn as a half–man half–horse creature, known as a centaur, with a bow and arrow in its hands. The lower two stars Rukbat and Arkab represent the creature’s left foreleg.

As usual with ancient constellations, a lot of imagination is neeeded to see this group of stars as a centaur. Instead, to modern eyes some of the brighter stars of the constellation clearly outline a teapot. The stars Kaus Media, Kaus Australis and Alnasi represent the spout, the stars Kaus Media, Kaus Borealis and the star to the right of Nunki represent the lid while Nunki, the star to its right, Ascella and the star to its left represent the handle. Once seen in this way the constellation becomes quite unmistakeable.

The brightest star of the constellation is Epsilon Sagittarii or Kaus Australis, meaning the Southern Bow. It is a hot white star that is 140 light years from us. Delta Sagittarii is known as Kaus Media, meaning the Middle of the Bow. This is an orange coloured star at a distance of 300 light years.

A few other stars of Sagittarius:

Gamma Sagittarii or Alnasi, meaning the point. It is an orange coloured star at a distance of 100 light years.
Zeta Sagittarii or Ascella, meaning the Armpit. It is a double star in which the components take 21 years to circle each other. The stars are 90 light years away.
Sigma Sagittarii or Nunki, meaning the Star of the Proclamation of the Sea. This wonderful name seems to refer to the fact that the following zodiac constellations, Capricornus, Aquarius and Pisces, are all associated with to water. It is a hot blue-white star that is 224 light years away.

The constellation contains a number of nebulae. One of these is the famous M8 or the Lagoon Nebula that is a huge cloud of gas and dust illuminated by a cluster of newly formed stars. Another famous object in Sagittarius is M20 or the Trifid Nebula that has three clearly visible dark lanes of dust in front of the bright part of the nebula.

Sagittarius is an excellent target through binoculars or through a small telescope. On a clear evening go outside and have a look!

The Adler Planetarium in Chicago on 5 July 2011. Courtesy nvidia.corporation

Last week on the beautiful summer day of Tuesday 5 July 2011 I made my third visit to one of my favourite places on Earth, the Adler Planetarium in Chicago. Located on the lakeshore with a wonderful view of the Chicago skyline, expectations are high even before stepping inside the building. On this visit my perspective was different to previous ones as we were accompanied by two young boys so that it was their reactions that guided what we saw and did.

First up was the main planetarium show currently showing, Journey to the stars, which is narrated by Whoopi Goldberg. To my jaded eyes the show was spectacular, but humourless and made the common planetarium show mistake of trying to cram in far too much information. The young boys, who had never seen anything like it previously, loved it though, at least once the younger one overcame his fear of the dark. They said that the show was ‘cool’.

Soon after there was another show in the same planetarium theatre, Night Sky Live! This time even I was impressed and the boys were enchanted. A live guide, who introduced himself with the easy-to-remember name of Nick, presented the northern summer sky as seen in light polluted Chicago. Nick used humour, spoke at the right level and asked questions from the audience who shouted back their replies. With a remote control he could call up spectacular pre-programmed effects on the dome. The show reinforced my belief in the importance of human presenters in planetariums.

The Atwood Sphere at the Adler Planetarium photographed in June 2000. Image and copyright Nick Lomb ©, all rights reserved

The two planetarium shows were followed up with a visit to the Atwood Sphere. This is the oldest planetarium in Chicago and consists of a 4.5-metre wide sphere with over 600 holes drilled in its skin to represent the stars as seen locally. There is now a small carriage that takes visitors up into the continually rotating sphere for a 10-minute guided tour of the sky. It is a good experience though I was a little disapponted in the guide C—. He didn’t seem to have a talk ready, but begged the eight or so people in the carriage for questions to fill in the time until the summer sky rotated into view. And when he was asked questions he seemed to mix up black holes and neutron stars in his answers. Not that anyone else but an astronomer would have noticed.

After a picnic lunch outside in the park, in which feeding a duck and the seagulls was the highlight, it was back inside the planetarium, this time to explore the exhibits. There was interest in some of these, but when we discovered the relatively new children’s exhibition Planet Explorers, there was great excitement. There was so much to do in this exhibition, which is beautifully geared to 3 to 8-year old children, that we only managed to see part of it. The first highlight was driving small rovers called X Movers on the surface of Planet X. The two boys were in their element in controlling one of the rovers and with separate controls to move forwards and backwards and to steer, they could even cooperate with each other.

The other exhibit in Planet Explorers that grabbed their attention was a large format screen showing an Earth map in which they could try to zoom in on their own home in Chicago. In the four minutes allocated to each user they did not quite succeed, but that did not stop them from trying again, again and again.

Overall, it was a great day at the Adler that was enjoyed by all. And I learnt once again the importance of aiming planetarium shows and astronomy exhibitions at all age groups.