Sky-High 2017
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Sky-High 2017 Total Solar Eclipse, 13th Nov 2012 This is the 25th annual guide to astronomical phenomena visible from Ireland during the year ahead (naked-eye, binocular and beyond) Editor: John O’Neill Published by the Irish Astronomical Society € 5 (Phone: 087-6398143) [email protected] www.irishastrosoc.org Page 1 Foreword Contents We send greetings to all fellow astronomers and 3 Your Night Sky Primer welcome you to this, the twenty-fifth edition of our annual almanac for Irish Observers, Sky-High. 5 Sky Diary 2017 We are always glad to hear what you liked or what 9 Phases of Moon; Sunrise and Sunset for 2017 you would like to have included in Sky-High. And if you would like to clarify your understanding of 10 The Planets in 2017 anything feel free to contact us at the Society e-mail 13 Eclipses in 2017 address: [email protected]. Any updates or errata for Sky-High will be posted on the Sky-High 14 Comets in 2017 2017 web page (see page 27). Please acknowledge any use of Sky-High 2017. 15 Meteors Showers in 2017 The times of sunrise, variable star minima etc. are 16 Asteroids in 2017 from software by J. O’Neill. The charts were 17 Variable Stars in 2017 generated using Guide 9.1. LPV maxima are by Elizabeth Waagen (Senior Technical Assistant, 18 Featured Variable Star – CH Cygni AAVSO). 20 Mapping Irish Astronomy We thank the following contributors for their articles: Patricia Carroll, James O’Connor and Liam Smyth. The 22 When Astronomers Put the Saddle on the remaining articles were written by the Editor. Also Wrong Horse thanks to Sara Beck, Patricia Carroll and Liam Smyth 25 The Probably Impossible, the Improbably for proof-reading. Special thanks to Liam Smyth who Possible has retired as the Associate Editor of Sky-High. 26 Space Science Missions 2017 Wishing you clear skies for 2017, 27 Useful web sites Editor, John O’Neill 28 Gallery Sky-High 2017 © IAS, 2016 The Irish Astronomical Society The Irish Astronomical Society was founded in The Society also has a well stocked library of 1937. It caters for those of all ages and interests in books, journals and videos that members can bor- astronomy and space. row as well as access to a number of telescopes that can be loaned for a period. You don’t have to be an expert to be part of our Society. Many of our members are taking their first A number of IAS members have made their own steps in the hobby and you are sure to receive telescopes, while others possess telescopes ranging friendly advice from some of the more experienced in size to well above 50 cm aperture. Many are now amateur astronomers among us. experimenting with the latest technologies to hit the amateur community such as robotic tele- Activities include monthly talks, receiving our scopes. quarterly magazine Orbit, observing groups, e-mail alert notices of transient astronomical phenomena If you are considering purchasing a telescope then such as aurora, and outings to places of astronomi- we’ll point you in the right direction before you cal interest. part with your hard-earned cash. Members have joined expeditions to observe sev- The Dublin Sidewalk Astronomers (a group within eral total solar eclipses world wide. Also note, the the IAS) hold public star parties at regular inter- printed Sky-High is a free benefit of IAS vals, usually by the seafront at both Sandymount membership. and Clontarf in Dublin (see IAS website for details). Page 2 Your Night Sky Primer As with any hobby, astronomy seems to have its a small telescope, you will need a more detailed own set of terminology designed to confuse. How- map showing all stars to at least sixth magnitude. A ever, with a little patience you'll soon pick up the handy atlas is the Pocket Star Atlas published by jargon and be well on the way to knowing your way New Track Media (for about €15). This shows stars to around the sky. magnitude 7.6 and the positions of many deep sky objects. The revolving heavens We all know the Heavens don't revolve. It is the An idea of size or scale other way round, the Earth rotates on its axis. But If you have seen a picture of a total eclipse of the it looks otherwise and it is easier to describe things Sun you will have noticed that the black disk of the as we see them for our immediate purpose. The Moon just about covers the bright disk of The Sun. If fact that the Earth turns on its axis about every 24 you were to suspend a one Euro coin about two and hours causes the Sun to rise in the east and set in a half metres in front of your eye, it would just the west, and it is due south at noon. A similar about cover the Moon's disk. situation applies to all the other heavenly bodies except that since they appear to move relative to The Sun is nearly 1.4 million km in diameter, the the Sun they are not south every day at noon. Moon is 3476 km and the one Euro coin is just over two centimetres in size. Yet they appear nearly The stars appear to drift west in such a way that equal. This is because they all seem to take up the any particular star is due south four minutes earlier same amount of the space in front of our eyes. We each day or night. If you multiply four minutes by may say they have the same angular diameter. In 365 you get something close to 24 hours. So if a this case it is about half a degree (½°). star is south at eight o'clock tonight, it will be south four minutes earlier tomorrow, and two Degrees are further divided into 60 arcminutes (60') hours earlier in a month. In six months it will be with each arcminute made up of 60 arcseconds south at about eight in the morning. In a year it (60"). The scale allows us to measure angles in the will again be south at eight in the evening. It fol- sky or the apparent size of a celestial object. For lows that we see different constellations in differ- example, the Full Moon measures an average of ½° ent seasons, but over a year, we see all that por- or 30', in diameter. tion of the heavens that can be seen from Ireland. Your closed fist held at arms length is about ten de- Star maps grees (10°). Your stretched out hand, i.e. from the You will need at least one star map. This could be tip of your thumb to the tip of your little finger, is a set of monthly charts such as are included in about twenty degrees. Between four and five out- many books on astronomy. A Planisphere is very stretched hands or twice as many closed fists will useful. They come in various sizes at equivalent take you from the horizon to zenith. If you know the cost. It allows you to show the constellations visi- Plough you will find that its overall length is rather ble at any time of the night, any time in the year. more than one outstretched hand - it is almost 25°. You could get away with using the monthly charts Some familiarity with angular measure is necessary published in newspapers but there are a couple of to find your way easily about the sky. drawbacks. Each chart is correct for only one time on a given night, say 10 p.m. If you are observing Positioning in the sky two hours later you would need the following Starting at any landmark and going right around the month's chart. These charts also show the planets horizon is three hundred and sixty degrees. The azi- visible for a particular month, so they can be con- muth of an object is a measure of its position rela- fusing unless you tippex them out. When learning tive to the horizon as measured from true north the constellations check first from the monthly which starts at 0° with due east being 90° and so notes if there is a bright planet in the area. on. Going from a point on the horizon straight up to the point overhead - the zenith - is ninety degrees Once you can find the constellations you will enjoy and a measure of altitude. learning more about them. Astronomers use a kind of celestial longitude and lati- A useful guide is the Collins Stars & Planets which tude called right ascension and declination to plot has constellation charts as well as all-sky charts, accurately the position of an object in the sky. The along with sections on the stars and planets. For basis for this system is the equator and the poles. more detailed studies, especially with binoculars or Page 3 Right ascension is expressed in hours (h), minutes A note on time (m) and seconds (s) running eastward from 0 to 24 Times throughout Sky-High are given in Universal hours around the equator. The zero point of right Time (UT), unless otherwise noted. This is the 24- ascension is taken as the vernal equinox - the point hour system starting at mean midnight as measured where the Sun crosses the celestial equator, moving at Greenwich. It is the same as Greenwich Mean from south to north, in its course around the sky.