Before the colloquium, light welcome snacks and beverages will be served, and there will be an optional screening of the planetarium film ‘Rising Star’ (see details below). Please arrive by at least 16:50 if you also wish to watch the film.

ASSA Special Centenary Colloquium 
DATE:   Friday 1 July, main presentation from 17:30 to 18:30 SAST
VENUE:   The Iziko Planetarium and Digital Dome.
25 Queen Victoria St, Gardens, Cape Town (Entrance via main Iziko SA museum entrance)
SCHEDULE:   16:30 Welcome snacks and drinks on arrival
17:00 – 17:25  Guests can continue to mingle or attend the screening of the planetarium film Rising Star
17:30 – 18:30  Special Colloquium: “Milestones in South African Astronomy” by Ian Glass (also live streamed on YouTube)

** Please fill in the Google Form to RSVP by Tuesday 28 June:
https://forms.gle/8Sz8tYdVDJ5AeAXk6

If you have any questions, please contact Sally Macfarlane at sallymac@gmail.com

We look forward to seeing you on the 1st of July!

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Rising Star is the first digital planetarium film of its kind to be produced in Africa about South African astronomy.

This film will take you on an astronomical journey from our beginnings through the development of astronomy research in South Africa to what the future holds for the country and will introduce you to multi-wavelength and multi-messenger astronomy! It will highlight the many remarkable facilities hosted in South Africa, including the Southern African Large Telescope and the most powerful radio telescope in the Southern Hemisphere, MeerKAT.

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23 June 2022

Bright fireball seen from the Western Cape on Saturday 18 June 2022 by Tim Cooper

Several hundred tonnes of solid particles enter Earth’s atmosphere every day.  Most of these are small particles left behind by comets as they round the Sun.  Particles travelling through space are called meteoroids.  Particles entering the atmosphere at high speed, typically 20-70 km/sec, become visible as meteors (or popularly as ‘shooting stars’) and burn up before they reach the ground.  Very bright meteors are called fireballs, and those that are seen to explode are called bolides.  If the object survives its passage through the atmosphere and reaches the ground it is called a meteorite.  These objects are much larger than ordinary meteors and are due to entry of fragments of asteroids into the atmosphere.

During the early morning of Saturday 18 June, a small fragment of asteroid entered the atmosphere resulting in a very bright bolide, which was widely seen over the Western Cape’s Garden Route region.  This is the fourth very bright fireball seen over the Western Cape in recent years.

Time and duration

Most reports gave the time as 05h47 SAST.  One observer confirmed this time from a GPS, so it can be considered as correct.  Some videos were posted online which showed time stamps with a different time, but these time stamps are taken from PCs which were uncalibrated and therefore unreliable.  Many gave the duration of the passage of the fireball as three to four seconds, but again the attention of most people was only drawn to the presence of the fireball by the very bright flash, at which point the object disrupted.  There were probably few sightings of the object when it began its fiery path in the upper atmosphere at about 120 km altitude.

Brightness and colour

The brightness of very bright fireballs is always subjective, as there are few bright objects with which to compare.  Most comparisons are made against the sun, or full Moon, neither of which was visible at the time, thought the 82% illuminated Moon was high in the north at the time.  Estimates of the brightness were between 50-100 times the brightness of the Moon.  Various colours were reported and included nearly the entire spectrum from red, orange, yellow, green and blue, and bright white.  There were many reports of bright green, which is typical of bright meteors, becoming red as the object descended towards the horizon.

Fragmentation, persistent train and sounds heard

Most agreed that the object exploded during its path, splitting into numerous fragments.  One observer said there were four or five large fragments, and another said there were more than 50 smaller fragments.  There were no reports of any smoke train left behind after the fireball disappeared.  Only two people said they heard sounds, one like a crack, the other three distinct explosions.

Path of the fireball

From various reliable eye witness accounts we reconstructed the path of the fireball as shown by the yellow arrow.  The fireball was first seen just south and perhaps west of Mossel Bay. The yellow arrow may have started further to the west, but was only really noticed around the time of the bright flash, by which time it was south of the coast.  The fireball burned out and entered ‘dark flight’ at which stage it had been slowed down to the extent that it no longer caused visible light, around 120 km to the south, and perhaps slightly east of Plettenberg Bay.

Conclusion

A small fragment of asteroid entered the atmosphere on Saturday 18 June at 05h47 SAST, resulting in a bright fireball visible to the south of the Garden Route.  The object disrupted in a bright flash, leaving several fragments which continued and burned out to the south of Plettenberg Bay.

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7 May 2022
ASSA Symposium from 14-16 October

As part of the 100-year celebrations, ASSA will be hosting a Symposium from 14-16 October 2022 hosted at the SAAO in Cape Town.

This will bring together amateur astronomers and professionals from across South Africa. With a series of presentations and ample time for discussion, it will provide the opportunity not only to reflect on ASSA’s achievements in the past 100 years but also on how ASSA will stay significant and progress in these days of big data astronomy.

Registration and the call for abstracts are now open at

https://symposium2022.assa.saao.ac.za/

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7 May 2022
ASSA launches 30 Under 30 project

ASSA is launching a Special Project entitled 30 Under 30 to identify young astronomers in Southern Africa and support their research and careers.

ASSA will publish a list of 30 young astronomers from Southern Africa, with details of their accomplishments and specific research interests. The list will include Master’s and PhD students or young professional astronomers, under the age of 30 and highlight and support their work through:

• Publishing in the Monthly Notes of ASSA
• Inviting them to speak at the ASSA 100 Symposium
• Connecting them with employment and research opportunities in SA and globally

Both individuals and institutions are encouraged to nominate promising young individuals at the below link:

https://assa.saao.ac.za/30-under-30/

Self-nominations are welcome.

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18 April 2022
QZ Carinae paper by David Blane

I recently participated in a mammoth international collaboration to improve our understanding of the enigmatic multi-star system, QZ Carinae. I am pleased to report that the paper has been accepted by Astronomy & Astrophysics and will be published in due course. This is the third publication on this eclipsing binary system we have published in recent years!

The pre-publication details are available on arXiv:2204.07045.

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22 March 2022
Update of Clyde’s Spot by Clyde Foster

As some of you are aware, I was credited with the discovery of a new storm outbreak on Jupiter on 31 May 2020 which quickly became known informally as “Clyde’s Spot” amongst both amateurs and professionals in the pla/netary community. What was notable was the relatively rare occurrence of such outbreaks that have been observed in this region, Jupiter’s South Temperate Belt, and even more so the fact that the NASA Juno spacecraft would sweep over the storm two days later, capturing amazing images of the outbreak. Thanks to the resulting NASA press releases (“Clyde’s Spot on Jupiter” and “Juno returns to Clyde’s Spot”), “Clyde’s Spot” attracted quite extensive media and public interest. As much as my primary focus is on enjoying my planetary imaging, and contributing to the Planetary Science community, this was certainly some nice recognition of what I am doing.

Above Left: Clyde Fosters’ image of the spot — Above Right:NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill

In the nearly two years since, headed by members of the Planetary Science group at the University of the Basque in Spain, Clyde’s Spot has become extensively researched. This has been thanks to the amazing results produced from the NASA Juno PJ27, PJ33 and PJ34 flybys, Hubble Space Telescope imaging, NASA IRTF imaging, images from other professional facilities, and, not least of all extensive amateur high resolution imaging. Needless to say, I have tracked and imaged the development of Clyde’s Spot on every/ possible opportunity over this period.

Dr Ricardo Hueso and Peio Inurrigarro (Clyde’s Spot has been the primary focus of his PhD studies) have been the key drivers for the research in Spain.

I am delighted to say that the research has been captured in an extensive paper (+-50 pages, with an additional +-12 pages of supplementary information), and I received notification on 21 March, that the paper, following extensive peer review, has been accepted for publication in the respected Icarus journal. I am honoured to be included as a co-author for the paper, alongside some highly esteemed professional planetary scientists, and proud to have ASSA as my primary affiliation.

Above: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill

During the (lengthy and intense!) peer-review process, I always had a concern that there would be pressure applied to replace the term “Clyde’s Spot” with a more “scientific” term, based on classical Jovian notation. I am delighted to say that the term was readily accepted by the reviewers, and in doing so, I am proud to say that “Clyde’s Spot” has now been accepted into formal Jovian scientific literature. As an amateur astronomer, I am not sure if it gets much better than that!

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28 January 2022
New ASSA Logo

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21 January 2022
Comet C/2021 A1 (Leonard) – Kos Coronaios

I haven’t had much luck with documenting all the outbursts and tail disconnection events with comet A1 Leonard since it was visible from our part of the world. Cloudy skies was the main culprit, but I was fortunate enough though in imaging the separation of the dust and ion tail of the comet over a 24 hour period on the evening of the 19th & 20th January 2022 in the image below. The following image taken last night (20/01/2022) is annotated.

 

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28 December 2021
Comet C/2021 A1 (Leonard) in Southern African skies – Tim Cooper

Discovered on 3 January 2021 by Greg Leonard at Mount Lemmon Observatory, the comet was expected to be the brightest comet of 2021, and was predicted to peak at about magnitude 4 around closest approach to Earth on December 18.  After that it was expected to fade as it became visible in southern skies during the early evening from December 18 onwards.  But when it re-emerged from the solar glare it was clearly undergoing an outburst.  Two further outbursts occurred on December 20 and 23, both times resulting in the comet being visible to the naked eye from dark sky sites, and sporting a beautiful tail (image courtesy Kos Coronaios).  With perihelion occurring on 2022 January 3, at which time the comet comes under its maximum warming by the sun, further outbursts may still occur.

The graphic shows where to find the comet during the first week of January.  It should be easy to find just below the star Aldhanab (gamma Gruis, magnitude 3.0) in the constellation of Grus, the Crane.  During January evenings the comet sets earlier each evening, and will be lost in the solar glare again by mid-month.

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28 December 2021
Comet C/2021 A1 (Leonard) – imaged by Kos Coronaios

The image below is a stack of 24 x 40 seconds with EF200mm lens working at f2.8, taken on the 27 Dec 2021

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14 November 2021
Sky Guide 2022

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From Vesta to the Kalahari: tracing meteorites from asteroid 2018 LA by Tim Cooper

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9th August 2021
Bolide over the Western Cape

Several persons reported hearing sounds at around 1am on the morning of August 9.  Locations included Riversdale, Mossel Bay, Oudtshoorn, Boggoms Bay, George, Hartenbos, Klein Brak River, Wilderness and De Rust, spanning a horizontal distance of around 115 km.  The most westerly location where sounds were reported was Riversdale, where it was described as a rumble, like distant thunder.  The most easterly was from several observers in the environs of George, where the sounds were mostly described as rumbling like thunder.  From Oudtshoorn the sound was also likened to distant thunder.  Others said it sounded like an explosion, houses shook and windows rattled.

Only three visual sightings were received of the bolide.  The best description was received from Ted Nutting, who was outdoors at the time and saw the passage of a bright green fireball in a clear sky, duration about 4 seconds moving west to east, and disintegrated into four or five fragments with a bright flash before disappearing.  Sounds were heard about two minutes later, as up to four distinct ‘bangs’ and tailing off afterwards like the sound of a jet flying over.  Triangulation of the start and end points gives a tentative path from west to east, seen towards the north from George, but to the south from near De Rust, where the start and end azimuths were 230° and 180° respectively, traveling parallel to a rooftop, at altitude 60-70°.  Frankie Dos Santos saw the bolide through a window facing azimuth 330° from Hoekwil, near Wilderness.  He described the fireball as ‘very bright, much bigger than a normal shooting star’, moving left to right (towards north east) at an altitude of about 45°, and very fast with a duration of about a second.  The sky was overcast with thin patchy clouds and the appearance was like seeing car headlights through fog.  The bolide possibly began ablation near overhead and just south of Oudtshoorn, and disrupted in the vicinity above Kammanassie Nature Reserve.  Fragments may have fallen as meteorites near to the Kammanassie Mountain range.

In order to determine the fall location of possible meteorites, sufficient video footage is required which shows both the passage and disruption of the bolide, or shadows cast by the flash, which are in the anti-direction of the disruption.  Unfortunately, despite requests on various forums to check security cameras, only one clip was received, from Godwin Pangel in George.  The clip shows a brief very bright flash, with duration less than 1 second, and was followed 2m56s later by a booming sound.  The sky is seen to be mainly overcast at the time of the bright flash.  The video footage was calibrated against internet time to give the time of the flash as August 9, 01:00:30 SAST.  The time lag of the sound gives a distance to the flash of approximately 60km.

The event was not detected by NASA fireball detectors, neither were there any reports to the ASSA, AMS nor IMO reporting forums.  I conclude that a bright bolide passed roughly west to east over the Western Cape, disrupting with a bright flash, and with accompanying sounds.  Insufficient video evidence could be obtained that could have enabled determination of a strewn field site for meteorites.

Several misconceptions arose in the social media in connection with the event.  Firstly the statement on some social media pages that the event was a ‘skyquake’.  There is no accepted scientific definition of what constitutes a ‘skyquake’; rather it appears to be a loose term originating on the internet describing rumbling sounds from unexplained sources, including possibly the sonic boom from meteors.  Since the bolide was observed visually, the suggestion that it was a ‘skyquake’ is clearly of no consequence.

Secondly that the event might be linked to the Perseid meteor shower, which normally peaks during the night of August 11/12, and showed an unexpected surge in activity this year on August 14 at 10am SAST, the outburst lasting about two hours.  The August 9 event was not related to the normal activity or the outburst of the Perseids.  The Perseid meteor stream is known debris from comet 109P/Swift-Tuttle, and particles from comets are too small to produce effects like that witnessed over the Western Cape on August 9.  The radiant of the meteors in the constellation of Perseus only rises early morning and is highest before dawn, and even then the radiant does not rise above the horizon at any time as seen from the George/Mossel Bay area.  Finally, the radiant is located in the north-east in the early morning and cannot explain any meteor observed on a trajectory from west to east.

Thirdly the misconception that what was seen was a meteorite.  Particles travelling through space are termed meteoroids.  If they enter the atmosphere then the resultant streak of light is termed a meteor.  Bright meteors are termed fireballs, and if seen to explode they are called bolides.  If the object survives its passage through the atmosphere, reaches the ground and is recovered then it is termed a meteorite.  Since no videos were obtained to triangulate the path and hence no fragments could be found on the ground, the event on August 9 is classified as a bolide.

Possible path of the August 9 bolide.  Yellow pins are locations where sounds were heard, red pins are locations of the three observers who actually saw the bolide, green pin is the location of the one video which caught the bright flash.

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July 2021
Conjunction of Mars, Venus and the Crescent Moon on 11-13 July 2021

Shortly after sunset on the evenings of July 11 to 13, weather permitting, we should be able to see a fine conjunction (close approach) between Mars, Venus and the crescent Moon in the western sky. The trio will be closest on the 12th, as the Moon zips by. Such events are pretty to watch and present opportunities to capture a relatively rare sight photographically.

On the 12th, the sun sets at about 17h00 SAST (there will be some variance according to your location), with the planets reaching the horizon about two hours later. The Moon will set at approximately 18h25 on the 11th (and of course later on the following days, as it moves from west to east through the sky). During the intervening time between sunset and the planets setting, the sky will naturally darken progressively. Given the proximity of the celestial bodies to the horizon during that time, it should be possible to include interesting foreground detail illuminated by twilight.

ASSA invites all who are interested, to submit their photos of this event. The best three, as judged by Chris Stewart (ASSA President) and Martin Heigan (ASSA Imaging Section Director) will be featured in the 2022 Sky Guide (with the photographer of course being credited), and the photographers will each receive five copies of that Sky Guide.

Find out more about the photographic challenge 

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April 2021
The Botswana super-bolide and meteorites from asteroid 2018 LA

Meteorite MP-19, found by Tim Cooper in Central Kalahari Game Reserve on October 12, 2018. Image courtesy Dr Peter Jenniskens.

Almost three years since the entry of asteroid 2018 LA into the atmosphere over Botswana on June 2, 2018, the scientific results generated by sixty-six authors, collectively known as the ‘2018 LA Consortium’, and after an in-depth analysis of the recovered meteorites from 2018 LA, are now out in an article in Meteoritics and Planetary Science.

Discovered just a few hours earlier, asteroid 2018 LA entered earth’s atmosphere at 16h44 UT, and resulted in a bolide which reached magnitude -23 during its disruption at an altitude of 27.8 km.  The resultant explosion deposited meteorites over a strewn field located in the northern part of the Central Kalahari Game Reserve (CKGR) in Botswana.  Several videos were secured which captured the visible passage of the bolide, including the bright explosion, which enabled a precise determination of the location at which the disruption occurred.  The screen grabs at right show the passage as seen from a commercial property in Gaborone just prior to the disruption of the meteor.

Left: Screen grabs of the bolide from a security camera in Gaborone. Images reproduced with kind permission of Beverly Lombard.

ASSA’s Tim Cooper calibrated videos of the bolide to help determine the location of the strewn field and also calibrated the footage which enabled photometry and subsequently the construction of the light curve of the meteor.  An initial search during June 18-23, 2018 found one meteorite (MP-01), now referred to as Motopi Pan.  Following revised astrometry, a new search was mounted with a team comprising members from the Botswana Geophysics Institute, Okavango Research Institute, Department of National Museum and Monuments (Botswana), the Department of Wildlife & National Parks, the Astronomical Society of Southern Africa (ASSA) and under the guidance of meteor astronomer Dr Peter Jenniskens from the SETI Institute.  The search during October 9-12, 2018 found an additional 22 fragments of asteroid 2018 LA, all collectively known as Motopi Pan, and including fragment MP-19 (image top left) found by Tim Cooper on October 12, 2018.  The discovery of these fragments now enabled a complete characterisation of the meteorites from asteroid 2018 LA, and determination of its origin in the solar system.

Left: Rubria Crater on asteroid 4 Vesta, probable source of the meteorites from 2018 LA.  Image credit NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Following extensive analysis using multiple techniques, these show the Motopi Pan meteorite to be a HED polymict breccia derived from howardite, eucrite, and diogenite lithologies.

The findings and pre-atmospheric orbit are consistent with an origin for Motopi Pan at asteroid 4 Vesta, possibly from the 10 km crater Rubria (left image) during an impact ~22 Ma ago.

The full scientific results and findings can be found in the Meteoritics and Planetary Science article.  The full story of the appearance of the bolide, eye-witness accounts, analysis of video footage to determine the strewn field location, measurement of the brightness of the meteor, and the October 2018 search for meteorites from asteroid 2018 LA will appear in the June issue of MNASSA.

Members of the October 2018 search team which found an additional 22 fragments of the Motopi Pan meteorite.  Standing left to right Tim Cooper (ASSA), Oliver Moses (ORI), Mohutsiwe Gabadirwe (BGI), Thebe Kemosedile (ORI), Sarah Tsenene (DWNP), Kabelo Dikole (BGI), Mosarwa Babutsi (Botswana National Museum, Gaborone), kneeling Kagiso Kgetse (DWNP) and Peter Jenniskens (SETI Institute).  ASSA = Astronomical Society of Southern Africa, BGI = Botswana Geoscience Institute, ORI = Okavango Research Institute of the University of Botswana at Maun, DWNP = Department of Wildlife and National Parks.  Photo by team member Odirile Sempho.

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January 2021
Hunting Spectres on the Moon

As the line of day & night (the terminator) falls across the Moon, sunlight glints off terrain of high relief while leaving lower regions bathed in shadow. This interplay of light and dark can create striking and short-lived features, known as “clair-obscur effects”.

Some of these lunar moments have evocative names, such as “Cassini’s Moon Maiden” and “Gruithuisen’s Lunar City”.
The visibility of these fleeting events depends on the underlying terrain, the angle of the Sun’s light, and, of course, the visibility of the Moon from your location.

In the 2021 edition of the Sky Guide, the astronomical handbook for southern Africa, predictions are given for the visibility of the “Lunar X” (p 6). The effect occurs during each lunar month, but only the event on 2021 January 20 will be visible from South Africa.

Clair-obscur guru Dana Thompson has kindly also supplied information about spotting the “Curtiss Cross”. This effect was first recorded on 1956 November 26, by astronomy enthusiast Robert E. Curtiss (New Mexico, USA). The distinct formation lies near the crater Copernicus (see accompanying photographs).

During 2021, there are three opportunities to witness this spectral sight: 2021 April 06, June 04, and November 28.
Happy hunting!

2021 Jan 07 09:08
2021 Feb 05 23:42
2021 Mar 07 13:44
2021 Apr 06* 02:53
2021 May 05 15:04
2021 Jun 04* 02:28
2021 Jul 03 13:24
2021 Aug 02 00:20
2021 Aug 31 11:42
2021 Sep 29 23:48
2021 Oct 29 12:50
2021 Nov 28* 02:44
2021 Dec 27 17:14

Times in SAST

* Visible from         South Africa

 

 

 

 

 

 

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21 December 2020
Great Conjunction

Photo by Angus Burns, Newcastle KZN

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14 December 2020
Solar Eclipse

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‘Star of Bethlehem ‘ to light up SA skies – A bit of celestial wonder to end the year.

Prepare to witness a celestial event that’s been dubbed the “star of Bethlehem” in our night skies in the coming weeks. Dr Daniel Cunnama, a science engagement astronomer at the South African Astronomical Observatory, confirmed that a spectacular conjunction of Jupiter and Saturn on 21st December will be visible in South Africa. “You can look to the West just after sunset and you will see them over the next two weeks”.

According to the BBC’s Sky at Night magazine, the closest giant planetary “kiss” since 1623 will see gas giant planets Jupiter and Saturn just 0,06° apart.

“Our Solar System’s two gas giant planets have been edging closer in recent months, and on Monday, December 21 Jupiter and Saturn will be less than a degree apart in the night sky,” says the magazine.

The spectacular sight will be visible in clear skies across the world. Sky at Night said Jupiter and  Saturn won’t really be close to each other at all. “In fact, on that date — which also just happens to be the date of the December solstice — Saturn will be about twice as far from Earth as Jupiter will be.

“However, our line of sight from Earth will suggest otherwise, as we all get to witness (clear skies allowing) the closest planetary conjunction of Jupiter and Saturn that most of us are ever going to see. “Saturn and Jupiter appear to pass close to each other, as seen from Earth, every 20 years, and when they do we call it a ‘great conjunction’.”

If you see it, count yourself lucky.

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2022 Sky Guide Africa South

Now available from ASSA Centres or if you join as a country member

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A Bit of Sky Guide History

The first edition of this Sky Guide was published in 1946 and was known as the Astronomical Handbook for Southern Africa. It consisted of 12 pages and was available for 1/6 from Juta and Co., Darling Street, Cape Town. Dr Richard Hugh Stoy of the Royal Observatory carried out most of the calculations, assisted by Mr Reginald de Kock, Dr Alan Cousins and other members of staff. In 1957 the book was redesigned and most of the calculations were performed by the Transvaal Centre’s Computing Section. In 1962 the Handbook was sold for 25 cents, and the Royal Observatory was again responsible for generating the data. In 1974, Dr Tony Fairall at the UCT Astronomy Department took over as editor. The next 13 issues were edited by Mr Rupert Hurly until Ms Pat Booth took over in 1990. During 2003, a committee consisting of Auke Slotegraaf, Maciej Soltynski and Cliff Turk, assisted by many helpers, redesigned the Handbook. After much deliberation the name was changed to the Sky Guide.

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Big 5 of the African Sky

^{Published 2017 June 23}
The Big 5 of the African Sky – the five best deep-sky objects – are beautifully placed at this time of year for observing.

Find out more about the Big 5 and how to observe them and also how to qualify for this beautiful personalized mug!