February - Astronomical Society of Southern Africa


February - Astronomical Society of Southern Africa

canopus february 2010assa johannesburg centre announcementsEnquiries to Alec Jamieson: 082 654 5336 or alec.jamieson@telkomsa.netSaturday 30 January 11 to 4 pm: Work Party and BraaiWork Party to clean up the telescope domes followed by a braai andtest-viewing through the telescopesThere is work to be done to clean up the telescope domes and check thefunctioning of the telescopes. Some wooden doors have been exposed to theelements and have swollen, making opening and closing difficult. Some carpenter'stools such as plane, sanding machine etc would be useful. There is also a lot of grassaround, and a few weed-eaters would deal with it nicely. A hedge is very overgrownand some gardener's secateurs would be very useful.If you are feeling energetic and useful, come along and help get the domes andtelescopes sorted ahead of our Mars Viewing Evening on Friday 12 February.-------------------------------------------------------------------------------------------------------Friday 12 February, from 6 pm: Mars Viewing EveningMembers and Visitors very welcomeThe telescopes in the Papadopoulos and Jacobs domes on the Observatory hill willbe opened. We also plan to have our donated 12" Meade SCT set up under thestars on the Observatory hill.Mars is near to its shortest distance from Earth, and this is a good opportunity to seewhat surface details on Mars can be revealed by our telescopes. Mars is now abright object, conveniently located in the early evening sky.For inexperienced visitors there will be a laser What's Up to point out the mainconstellations and objects of interest visible in the sky during the evening.With electricity reconnected, there will be lighting in all of the buildings, including thenearby toilets. The telescopes and domes will be able to operate normally, and hotwater, tea and coffee will be available in the kitchen of the Herbert Baker Librarybuilding close to the telescope domes. Visitors can pack a picnic supper, or putsomething on the fire provided for a bring-and-braai.Come and enjoy our first back-to-normal viewing evening for several years.-------------------------------------------------------------------------------------------------------page 5

canopus february 2010melvyn on the monthly meetingby melvyn hannibal13 January: After Gary's welcome, Kobie gave us a very well illustrated fairy taleabout what some people believe is above our beloved, protecting, and everlastinggrey boundary to our universe.The main speaker was centre member EdmondFurter on the subject of Archeo-astronomy. This is asubject open to different interpretations by differentpeople. It deals with providing a link betweenancient drawings by past civilizations and how theysaw the patterns in the sky as opposed to the"classic" constellations in use by European basedsocieties today.Edmond's talk was very well illustrated, and couldhave made use of a longer time allocation. Therewere a number of diagrams, that I'd have liked tolook at, but time ran out.Thank you, Ed.MelvynPS: While I was in Cape Town recently: I decided to follow Magda's (Streicher)visits to two astronomical sites in the city.(See MNASSA v 67 3&4 April 2008): Herschel Monument:This proved to be less that straightforward due to aschool now called Grove Primary, and the street namesare not very well placed. Being school holidays, wecould only view the obelisk through the fence.The plaque to Abbe Lacailleproved a bit more difficult tolocal, and it was only after mycousin telephoned Cliff Turk, thatwe found it next to the BargainBooks doorway in between StGeorge's and Adderley streets. Itis now reasonably clean, but verymuch in need of a polish.page 6

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canopus february 2010diarise and offer your help17 APRIL 2010Military History Museum – SaxonwoldWant to offer some ideas, exhibit or come and help on the day?Contact us: mail Lerika@icon.co.zaKeep an eye on www.scopex.co.za-------------------------------------------------------------------------------------------------------Southern African Ninth Biennial Astronomy Symposium7 and 8 October 2010The Pretoria branch of ASSA is proud to announce the dates for the Southern AfricanEighth Biennial Symposium of the ASSA. The symposium will take place at the Silvertoncampus of the Council for Geoscience on Thursday 7 October 2010 and Friday 8October 2010. The preliminary program for Saturday includes a morning visit to HartRAOand a guided tour through the Tswaing meteorite impact crater during the afternoon.The symposium will focus on light/spectrum pollution and people interested in deliveringpapers are invited to send a short synopsis to Andrie van der Linde atandrie@eridanusoptics.com. You can also make a preliminary booking if you plan toattend. Details on registration fees and suggestions for accommodation, etc will beavailable soon.page 10

canopus february 2010matters and mutters – February 2010by bruce dicksonContrastFor our purposes, it will suffice to define contrast as a measure of how well the objectbeing observed stands out against either noise – in the form of a bright surroundings – orother objects in the field of view.As I pointed out before, stars don’t appear to get dimmer when you increasemagnification while extended objects do. The sky is an extended object, so if you wishto observe stars, magnification can be your friend. Of course you really have to temperthis by not overdriving the optics or more probably the seeing, but most scopes cantolerate 30x per inch of aperture.That said, I have a friend living north of here who regularly drives his scope to 75x per inchwhen observing double stars. I have heard of a 10” Maksutov being driven to 1000x by ahighly respected observer.Guidelines are just guidelines. It’s often a good idea to test them and see whether youconcur. Getting it wrong can be expensive, so I suggest you test the common wisdomby borrowing eyepieces.To resume – suppose you want to split Antares and its companion [1]. This binary systemhas one component which is cool, red and bright and another component which is hot,blue and 370 times dimmer. Increasing magnification doesn’t really work because evenwith a perfect telescope under perfect skies, the bright component still causes a lot ofscatter inside the observer’s eye.Now stars are essentially black body radiators – things that appear to be red don’t makemuch blue light and things that appear to be blue don’t appear to be red [2]. (They dogenerate red light, just relatively less of it.)To pull out Antares B, you can exploit this by inserting a deep blue filter into the light path.This suppresses light from the primary star so much that the second component pops intoview. This trick gave Magda and I our first view of the double. Like all things, it’s easyonce you know how.This leads me to the crux of this discussion.There are just two affordable ways to enhance contrast. First you can suppressbackground light by increasing the magnification. Second you can subtract light using afilter. Both approaches result in a dimmer image.page 11

canopus february 2010The second part of this is what to do when the object you want to observe is extended.Magnification cannot work because the object will get dimmer just as rapidly as the skydoes… and anyway a lot of pretty things are fairly large so magnification is undesirable.Well here technology comes to the rescue. Next month will be about narrow bandobserving.1. http://en.wikipedia.org/wiki/Antares2. http://en.wikipedia.org/wiki/Black_bodyBruceToronto, winter 2010for the fun of itAsteroid naming competition: public internet votingSAAO/SALT is conducting an asteroid naming competition where Dr. Amanda Gulbisoffered an opportunity for youth in South Africa to suggest a name for an asteroid shediscovered. More than 100 names were suggested and a selection committee at SAAOchose top five names -- Ubuntu, Jabulani, Mzanzi, ILITYE, and isiqobo.And now the general public may elect the winning name from these. Visit the website –http://www.nameourasteroid.org.za/ and vote by 31 January 2010.Everybody is welcome to take part. The winning name will be announced on 1 February.There will be a lucky draw – you could receive a SAAO/SALT gift hamper.Sky & Telescope: All 68 Years of It !December 29, 2009: A unified index for all 68 years (and 2 months) of Sky & Telescope isnow available online.Read More at:http://www.skyandtelescope.com/community/skyblog/newsblog/80282957.htmlgetting started in AstronomyTo help spread the word that backyard astronomy is easy and fun, the Sky andTelescope offers a free Getting Started in Astronomy pamphlet is available as adownloadable 10-page, black-and-white Adobe PDF file suitable for printing andphotocopying.page 12

canopus february 2010It comes in two versions: one for stargazers in the Northern Hemisphere and another forthose in the Southern Hemisphere. Each version contains the following:• "Your First Steps in Astronomy," offering simple tips for starting out right and avoidingfrustration• "Finding Your Way Among the Stars," with helpful instructions for using naked-eyestar maps• Six bimonthly charts of the stars and constellations visible in the evening skythroughout the year• "Exploring the Moon," with a lunar map suitable for use with binoculars or theunaided eye.Download your fee pamphlet athttp://www.skyandtelescope.com/howto/basics/3308331.html?c=y&page=1how to start right in astronomyDid you know you can see a galaxy 2½ million light-years away with your unaided eyes?Craters on the Moon with binoculars?The first step is simply to look up and ask, "What's that?" When you do, you're taking thefirst step toward a lifetime of cosmic exploration and enjoyment.But what, exactly, comes next? Too many newcomers to astronomy get lost in deadends and quit in frustration.What advice would help beginners the most? A while ago, the Sky & Telescopeeditors got together to brainstorm this question. Pooling thoughts from more than 100years of collective experience answering the phones and mail, we came up with thefollowing pointers to help newcomers past the most common pitfalls and onto thelikeliest route to success.1. Learn the sky with the unaided eye.2. Ransack your public library.3. Thinking telescope? Start with binoculars.4. Dive into maps and guidebooks.5. Keep an astronomy diary.6. Seek out other amateurs.7. When it's time for a telescope, plunge in deep.page 13

canopus february 20108. Lose your ego.9. Relax and have fun.Learn to take pleasure in whatever your instrument can indeed show you. The moreyou look and examine, the more you will see — and the more you'll become athome in the night sky. Set your own pace, and delight in the beauty and mystery ofour amazing universe.Read full article at http://www.skyandtelescope.com/howto/basics/3304616.htmlyour dates with marsWednesday, January 27Mars is closest to Earth, appearing bigger through a telescope (14.1 arcseconds) thananytime from 2008 until 2012. It remains essentially the same size for another week or two.This is an unfavorable showing as Mars apparitions go, however; Mars reached anapparent diameter of 25.1″ in August 2003 and will be 24.3″ in July 2018.Thursday, January 28The nearly full Moon this evening is accompanied by Pollux and Castor to its upper left,Procyon to its lower right, and Mars farther to its lower leftFriday, January 29Mars is at opposition, opposite the Sun in Earth's sky. So is the full Moon next to it!Moreover, the Moon is at perigee, making this the largest and brightest full Moon, by alittle bit, of the year. (The Moon is exactly full at 1:18 a.m. Saturday morning EST).Saturday, January 30Mars shines above the Moon this evening, by about 1½ fist-widths at arm's length. Muchcloser to the Moon's lower left, look for Regulus.telescope in south Africa wins prestigious awardhttp://www.superwasp.org/The Wide Angle Search for Planets experiment, SuperWASP, which has a telescopelocated outside the Karoo town of Sutherland at the South African AstronomicalObservatory has won the Group Achievement Award for Astronomy presented by theRoyal Astronomical Society (RAS). The RAS, the UK's voice for professional astronomers,annually presents a number of prizes honouring individuals and groups who have madean outstanding contribution to astronomy and astrophysics. The prizes will be presentedpage 14

canopus february 2010at the 2010 National Astronomy Meeting (NAM 2010) to be held in Glasgow betweenthe 12th and the 16th of April.SuperWASP has so far detected 18 planets in orbitaround stars other than the Sun (extrasolar planets orexoplanets). This planet search experiment uses twoclusters of 8 cameras, one on La Palma and one inSouth Africa, watching for characteristic dips in thebrightness of stars as planets pass in front of them.Despite their modest resources, the team havemade a world-class contribution to exoplanetscience. Of the 18 planets detected, 10 were foundfrom South Africa. The S.A. Astronomical Observatoryin Sutherland has among the darkest night skies ofthe many observatories around the world, whichcritically aids in the detection of the minute changesin the brightness of the stars due to their orbitingplanets.SuperWASP is a consortium of 8 academic institutions: the University of Cambridge, theIAC, the Isaac Newton Group of telescopes, the University of Keele, the University ofLeicester, the Open University, Queen's University Belfast and St Andrew's University.canopus 25 years ago …Canopus Vol 3, Number 6; January 1985DECEMBER SOCIAL EVENINGDue to some communication problems with the CSIR we very nearly were preventedfrom having the social evening that we had planned. However, thanks to some hardwork by Danie Overbeek and Ivan Myers, who visited the officials concerned at the lastminute (almost), the evening went ahead and turned out to be a tremendous success.Thank you to all the members who came along and made the evening as pleasant as itwas.The people who were there took part in a minor historical event in that they were able tolook through the newly-erected Jacobs telescope for the very first time. Although theweather was patchy, all agreed that the optics are excellent and that this telescope isgoing to be a valuable asset to the society. Don Michie put in a tremendous amount ofwork to get this telescope assembled in time. Thank you Don.Submitted by the editor of canopus at the time: brian fraserpage 15

canopus february 2010what’s upby christopher middletonThe Clouds of MagellanReference source: The Night Sky Observers Guide Volume 3The Clouds of Magellan are named after the Portuguese navigator of the 16 th century.The Clouds were however discovered many years before by other sailors who navigatedtheir way around the Cape of Good Hope. The two clouds are two galaxy satellites ofour galaxy The Milky Way and were, for many years, known as the Cape Clouds.Both the Small and Large Magellanic Clouds are beautiful when scanned withbinoculars or under more intense scrutiny with a telescope. Even small telescopes show aplethora of open clusters along with easily distinguished globulars.Relatively speaking the Clouds are close by (Large Magellanic Cloud about 190 000 lightyears away and the Small Magellanic Cloud 200 000 light years distant) which hasresulted in many of their open, globular and nebulous regions been given their own NGCand IC numbers. The general separation between the Clouds is about 80 000 light years.The abundance of beautiful objects within both Clouds makes a detailed descriptionimpossible. However, I present an object of extreme beauty. The Tarantula Nebula (NGC2070) within the Large Cloud is a large nebula centered upon the star 30 Doradus. Thenebula cloud is luminescent as a result of a cluster of fairly newly born supergiant starsthat can be compared to those in the Orion Nebula. The significant difference beingthat if the Tarantula nebula were as close as the Orion Nebula it would cover an area ofnearly 30 degrees in the sky!NGC 2070 taken with Starlight XpressSXV H9C and Meade SCT 12 inch at ~F/5Image: Christopher Middlletonpage 16

canopus february 2010sharon’s APOMSharon Tait shares with us her favourite Astronomy Picture of the Month…Dunes of MarsImage Credit: NASA/JPL-Caltech/University of ArizonaDunes of sand-sized materials have been trapped on the floors of many Martiancraters. This is one example, from a crater in Noachis Terra, west of the giant Hellasimpact basin. The High Resolution Imaging Science Experiment (HiRISE) camera onNASA's Mars Reconnaissance Orbiter captured this view on Dec. 28, 2009.The dunes here are linear, thought to be due to shifting wind directions. In places,each dune is remarkably similar to adjacent dunes, including a reddish (or dustcolored) band on northeast-facing slopes. Large angular boulders litter the floorbetween dunes.page 17

canopus february 2010Cover Photo: on the trail of a cosmic cathttp://www.eso.org/public/news/eso1003/20 January 2010: ESO has just released a stunning new image of the vast cloudknown as the Cat’s Paw Nebula or NGC 6334.This complex region of gas and dust, where numerous massive stars are born, liesnear the heart of the Milky Way galaxy, and is heavily obscured by intervening dustclouds.Few objects in the sky have been as well named as the Cat’s Paw Nebula, a glowinggas cloud resembling the gigantic pawprint of a celestial cat out on an errandacross the Universe.British astronomer John Herschel first recorded NGC 6334 in 1837 during his stay inSouth Africa. Despite using one of the largest telescopes in the world at the time,Herschel seems to have only noted the brightest part of the cloud, seen heretowards the lower left.NGC 6334 lies about 5500 light-years away in the direction of the constellationScorpius (the Scorpion) and covers an area on the sky slightly larger than the fullMoon. The whole gas cloud is about 50 light-years across.The nebula appears red because its blue and green light are scattered andabsorbed more efficiently by material between the nebula and Earth. The red lightcomes predominantly from hydrogen gas glowing under the intense glare of hotyoung stars.NGC 6334 is one of the most active nurseries of massive stars in our galaxy and hasbeen extensively studied by astronomers. The nebula conceals freshly minted brilliantblue stars — each nearly ten times the mass of our Sun and born in the last few millionyears. The region is also home to many baby stars that are buried deep in the dust,making them difficult to study.In total, the Cat’s Paw Nebula could contain several tens of thousands of stars.Particularly striking is the red, intricate bubble in the lower right part of the image. Thisis most likely either a star expelling large amount of matter at high speed as it nearsthe end of its life or the remnant of a star that already has exploded.This new portrait of the Cat’s Paw Nebula was created from images taken with the WideField Imager (WFI) instrument at the 2.2-metre MPG/ESO telescope at the La SillaObservatory in Chile, combining images taken through blue, green and red filters, as wellas a special filter designed to let through the light of glowing hydrogen.page 18

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