PRET ORI A CENT RE ASSA - NOVEM BER 2015 PAGE 1 NEWSLETTER NOVEMBER 2015 Next meeting Venue: The auditorium behind the main building at Christian Brothers College (CBC), Mount Edmund, Pretoria Road, Silverton, Pretoria. Date and time: Wednesday 25 November at 19h15. Programme: ♦ Beginner’s Corner:.”Dobsonian go-to project” by Michael Moller. ♦ What’s Up? by Percy Jacobs. ♦ ###################### 10 minute break . Library will be open. ##################### ♦ Main talk: “In Halley’s footsteps: a visit to the island of St Helena” by Michael Poll. * ♦ Socializing over tea/coffee and biscuits. The chairperson at the meeting will be Pierre Lourens. * See page 11 for a summary of his talk and some images illustrating it. Next observing evening Friday 20 November from sunset onwards at the Pretoria Centre Observatory, which is also situ- ated at CBC. Turn left immediately after entering the main gate and follow the road. Contents of this newsletter Summary of “What’s Up?” to be presented on 20 November 2015 2 Chairperson’s Report for the meeting of 28 October 2015 4 NGC 253: Caroline se Newel 6 Feature of the month: Cumulonimbus clouds and the white spots on Saturn 7 NOTICE BOARD 8 Astronomy-related articles on the Internet 9 Errata 9 Occultation of Uranus by the moon on 29 September 2015 10 Summary of the main talk to be given on 25 November 11 Halley’s mount 11 Jamestown 11 Basics: Sirius 12 Astronomy-related images and video clips on the Internet 13 Report for Observing Evening on 23 October 2015 14 Pretoria Centre committee & Pretoria Centre committee & Old newsletters & Database 12 PAGE 2 PRET ORI A CENT RE ASSA - NOVEM BER 2015 Summary of “What’s Up?” to be presented on 20 November 2015 - by Percy Jacobs What's up from December 2015 to January 2016: Phases of the Moon 1st Dec to 13th Dec and 1st Jan to 12th Jan Dark sky 3rd Dec – rises 00:24 and 2nd Jan – rises 00:05 Last Quarter 11th Dec and 10th Jan New Moon 18th Dec – rises 12:07 and 17th Jan – rises 13:08 First Quarter 25th Dec – rises 19:20 and 24th Jan – rises 19:36 Full Moon Planets Mercury – after sunset in the West 13th Dec - 17 above horizon not visible in Jan rises in the East at same day and time Venus – early morning looking East 13th Dec – 31 above horizon just before sunrise 27 above in Jan same day time Mars – early morning looking North East 13th Dec - 41 above horizon before sunrise 57 above horizon in Jan same day & time Jupiter - early morning looking North East 13th Dec – 53 above horizon before sunrise 59 above horizon in Jan same day & time Saturn – now seen just before sunrise in the East 13th Dec - 7 above horizon 31 above horizon in Jan same day & time 13th Jan - Saturn is above & close to Venus. Can be seen in the same Field of View with 8 x 50 binoculars Uranus (Pisces) & Neptune (Aquarius) – seen in the North & North West 13th Dec @ 20:30 – Uranus 56 above horizon (north) 13th Dec @ 20:30 – Neptune 41 above horizon (north west) Uranus is perfectly placed for getting a good view of this planet if you have not seen it before. ~Mag. 5.8 – can be seen with binoculars 13th Jan @ 20:30 – Uranus 38 above horizon (north west) 13th Jan @ 20:30 – Neptune 15 above horizon (north west) PRET ORI A CENT RE ASSA - NOVEM BER 2015 PAGE 3 Events Groupings 4th Dec @ 04:00 – Jupiter within 1 deg of the Moon 3rd to 8th Dec – Jupiter, Venus, Mars, Moon all visible in the East early morning sky 25th Dec, looking North East, the Pleiades, Full Moon & Hyades Star Cluster, NGC 2264, “the Christmas tree cluster” Meteor Showers Geminids – 14th Dec at max – 23:00 to 03:00 - ~50 per hr (could be up to 120/ hr) - radiant in Gemini constellation – looking north, ~looking ~30 up. Try those photographic skills and see if you can capture this meteor shower Comet C/2013 US10 – Catalina – 5th magnitude – binocular object – 23rd Dec @ 03:30 at about 20 above horizon below Virgo Constellations – shall be discussed in more detail at meeting Looking South Carina (Canopus) - “The Ship” Vela – “The Sail” Eridanus (Achernar) – “The River” Grus (Al Nair) – “The Crane) Pheonix – “The Pheonix” Hydrus – “The Water Snake” Looking East Orion (Rigel & Betalgeuse) – “The Hunter” Canis Major (Sirius) – “The Dog” Gemini (Castor & Pollux) – “The Twins” Looking North Pegasus – “The Flying Horse” Aries (Hamal)– “The Goat” Taurus (Aldebaran) – “the Bull” Perseus (Mirfak – double star) – “Greek Hero” Andromeda Galaxy and it’s satellite Galaxies M110 & M32 Latest Submission – Pretoria ASSA Asterisms Michael Poll – “The Wedge of Cheese” Comprises parts of Indus and Pavo. The bright star is Alpha Pavonis. The three in a row on the left, reading downwards are Gamma, Beta and Delta Pavonis. The star paired with Alpha Pavonis is Beta Indi, and the star at the tip of the wedge is Alpha Indi. PAGE 4 PRET ORI A CENT RE ASSA - NOVEM BER 2015 For the ASSA 100 Observers 25 objects over 8 weeks in Dec & Jan at say 3 per week – easy achievable objective Enjoy the holidays and get the telescopes out from under the covers! Chairperson’s Report for the meeting of 28 October 2015 by Michelle Ferreira The required announcements were made and all the visitors were welcomed and requested to provide an e-mail address to received a complimentary copy of the newsletter. Beginner's Corner was presented by Caroline Overbeek. She was introduced as a primary school teacher with 33 years experience, who loves teaching children about astronomy and has taken children to Scopex for the past three years. She loves imparting knowledge and had found an interest in the different interpretations to the stars in the sky, by another culture. She centered her presentation 'Flowers in the Sky' around the book by the same name, ‘Flowers in the Sky’ by Clarissa Hughes. The book describes the interpretations of the bushmen of what they ob- served in the sky. The bushmen, also known as the People of the Eland, believed PRET ORI A CENT RE ASSA - NOVEM BER 2015 PAGE 5 that the stars were the spirits of the animals and the ancestors. They had different tales of how the sun and the moon came to be. Truly an interesting look into their interpretations of constellations we know so well and so differently. Then Danie Barnardo did his What's Up presentation. An event to be mindful of, is the ‘king’ of meteor showers, namely the Southern Taurids, peaking on 6 and 7 Nov, being one of the most prolific showers. The best viewing time for the month would be from the 4th to the 17th Nov. The main talk of the evening, was presented by Prof. Barbara Cunow. She is a professional astronomer and was appointed at the University of South Africa from 1996 until 2009. She started firstly as a lecturer, then senior lecturer and finally As- sociate Professor. She obtained her PhD in astronomy in 1994 at the University of Munster in Germany. Currently she is an amateur astronomer and her main astro- nomical interests are long-term observations of Saturn, starting already in 1980 and taking images of the night sky with her DSLR. Her talk 'Nova delight: how to enjoy a stellar eruption' highlighted two bright novae in 2013, being Nova Delphini 2013 (V339 Delphini) in August and Nova Cen- tauri 2013 (V1369 Cen) in December with maximum brightness of magnitude 4.3 and 3.3 respectively. Nova means 'new star'. This occurence is a cataclysmic nu- clear explosion on a white dwarf, which causes a sudden brightening of the star. In a binary system consisting of a normal star, normally a giant and a white dwarf, hy- drogen-rich gas flows from the normal star to the white dwarf via an accretion disc. The material on the surface of the white dwarf gets hotter and denser, and eventually the hydrogen burning is termally unstable and rapidly converts into other heavier elements, e.g. helium and then creating an explosion of material on the sur- face of the white dwarf. The energy/light is blown into space and the rise to peak brightness can be gradual or very rapid. Maximum brightness can occur within a few days and can fade for several motnhs until it disappears. Nova Cygni 1975 (V1500 Cygni) was a bright nova occurring in 1975 in the constellation Cygnus. V1500 Cygni was discovered on August 29 and reached mag- nitude 1.7 on the next day. Thoughts on how to enjoy a stellar eruption was shared by Barbara. You can observe it with your telescope, see the eruption and watch it changing in bright- ness. Through observation the visual magnitude can be estimated and the data submitted to AAVSO. The observer can take pictures, thereby recording the erup- tion and compare it with images of the field of view before the outburst occured. The changing brightness and spectrometry can also be recorded. She then shared her notes and recordings of Nova Delphini 2013 and Nova Centauri 2013. It was most interesting to note the initial eruption and brightness of when she observed the no- vae compared to that of the initial observations when these were first discovered. It was also illuminating to be able to observe the light curve that occured from her ob- servations and the deductions that could be made thereafter. In her summary the main features of the two novae were that both faded quickly, the most common type of nova light curve occured, Nova Delphinus 2013 faded more quickly than Nova Centauri 2013 and Nova Centauri 2013 oscillated around the maximum.