CLICK HERE TO DOWNLOAD A "PRINTER FRIENDLY" PDF FILE VERSION (44KB) Knowle Astronomical Society Almanac 2008 Knowle Astronomical Society is pleased to present its annual review of significant astronomical events for the year ahead. We hope that beginners and experts alike will find it informative and useful. Every effort has been made to ensure accurate timings for these events from the vicinity of Knowle and Dorridge. It is recommended however that observers check exact local timings a few days beforehand (as well as the weather forecast!). Please note that when observing before sunset or after sunrise every precaution should be taken to avoid looking directly at the Sun using any form of optical instrument, including cameras and even the unaided human eye. British Summer Time All times in this almanac are quoted in Greenwich Mean Time (GMT). British Summer Time (BST) will be in force between March 30 th and October 26 th. To convert from GMT to BST add one hour to the quoted times. Sun and Moon
Equinoxes and Solstices
Eclipses On February 7 th a Solar Eclipse is visible from Antarctica and New Zealand . This eclipse is Annular from parts of Antarctica A Total Lunar Eclipse in the early hours of February 21 st is visible from the UK with the umbral phase lasting between 1:44 and 5:10 . On August 1 st a Solar Eclipse is visible from the Arctic , Northern Europe and Central Asia . This eclipse is Total from parts of the Arctic and Central Asia . From the UK the partial phase takes place between 8:33 and 10:07 . A Partial Lunar Eclipse on August 16 th starts shortly after moonrise, with the umbral phase lasting between 19:36 and 22:45. The Planets The best opportunities to see Mercury in 2008 occur in the evening sky for a couple of weeks around greatest elongation east on May 14 th and in the morning sky for a couple of weeks around greatest elongation west on October 22 nd. Venus continues its current morning apparition into 2008, but sinks gradually lower in the pre-dawn sky until it is eventually lost in twilight by the end of February. For most of the rest of the year it remains fairly close to the Sun in the sky and therefore difficult to observe. During November however it starts to climb into the evening sky above the north-western horizon and by the year end will be a brilliant and conspicuous object for several hours after sunset. Having reached opposition in late 2007 Mars continues to be a prominent evening object in Gemini throughout the first few months of 2008, although gradually fading in brightness and getting lower in the western sky. By the end of June it is lost in twilight and remains too close to the Sun to be well seen for the rest of the year. Mars does not come to opposition again until 2009. At the start of 2008 Jupiter is unfavourably placed, close to the Sun, but during January it starts to emerge into morning twilight. By the end of May it is rising before midnight and it reaches opposition on July 9 th. Jupiter then remains an evening object for the rest of the year. This year’s apparition is in the southernmost zodiacal constellation of Sagittarius and so the planet will not be well seen from our latitude. The occultations, transits and shadow transits of Jupiter’s Galilean satellites are easy to observe in small telescopes. It is very common to see one or even two transits or shadow transits in progress, but triple and other multiple events are much rarer. The only multiple events observable from the British Isles during 2007 are:- March 22 nd 03:58 – 04:42 Io transit & shadow transit, Ganymede transit June 16 th 00 :56 – 01:10 E uropa transit & shadow transit, Ganymede transit & shadow transit June 23 rd 02:40 – 03:44 E uropa transit & shadow transit, Ganymede transit September 9 th 18:41 – 19:45 Io transit & shadow transit, Ganymede transit. Callisto, the outermost satellite starts participating in these events again in 2008 after a few years of absence due to the unfavourable orientation of the orbital plane. However it is not involved in any multiple events this year. Saturn is a conspicuous evening object at the start of 2008 and reaches opposition on February 24 th in Leo. It remains an evening object until July when it is lost in twilight and will emerge into the morning sky again during September. By December it will be rising before midnight . Saturn’s rings continue to close during the year and will be edge on during 2009. Most of Saturn’s family of satellites orbit in roughly the same plane as the rings and during 2008 it will be possible to observe transits and occultations of all of the major ones except the largest, Titan. Uranus which, at magnitude 5.7, is only just visible to the naked eye under good conditions is at opposition in Aquarius on September 13 th and Neptune which, at magnitude 7.8, requires at least good binoculars to see, is at opposition in Capricornus on August 15 th. Conjunctions and Occultations The Moon encounters each planet during its monthly journey through the Zodiac. These conjunctions are often attractive sights, particularly those that occur at dawn or dusk when the Moon displays its crescent phase. Conjunctions between the planets are also reasonably frequent events. Sometimes the Moon will even pass directly in front of (i.e. occult) a planet or first magnitude star. Lunar occultations of fainter naked eye stars are fairly regular events. The following is a synopsis of the most notable conjunctions and occultations during 2007. On January 5 th the waning crescent Moon may be seen a few degrees below Venus before dawn. Towards the end of January Jupiter joins Venus in the pre-dawn sky. The distance between the two closes until on the morning of February 1 st they are less than a degree apart and then on February 3 rd and 4 th the waning crescent Moon is close to both of them. During February the separation between the two planets then increases again with Jupiter climbing higher whilst Venus sinks into twilight. The Moon is again close to Jupiter on the mornings of March 3 rd, March 30 th – 31 st, April 27 th and May 24 th and then in the evening sky on June 20 th, July 18 th, August 14 th, September 9 th, October 7 th, November 3 rd and December 1 st. Jupiter and Venus converge together again during November – this time in the evening sky. On December 1 st there will be an extremely interesting and attractive event when the four day old Moon occults Venus, with the planet disappearing behind the dark limb at 15:46 , about ten minutes before sunset and re-emerging from behind the bright limb at 17:17 . At the same time Jupiter is less than 2 degrees above the Moon. On December 31 st Venus is again close to the four day old crescent Moon. Following their very close encounter on Christmas Eve 2007 the Moon and Mars are again less than a degree apart on the night of January 19 th – 20 th. These two are also in conjunction on February 15 th – 16 th, March 14 th – 15 th, April 11 th, May 10 th and June 7 th. On the morning of February 27 th Venus is just over a degree from Mercury, but this will be a very difficult event to observe with both planets low down on the south-east horizon just before sunrise. There is a similar and equally difficult conjunction of these two planets in the evening sky on August 20 th. On May 6 th the one day old Moon may be seen less than two degrees from Mercury in the evening sky and on October 27 th the Moon is to the lower right of Mercury in the morning sky. The paths of the Moon and Neptune are very close to each other during 2008 and the two lie within a degree of each other on no less than thirteen occasions. Not all of these will be conveniently observed from the UK however. The best two events occur in the early hours of May 27 th (when the Moon is 6 arcminutes from Neptune at its closest approach at 3:01) and on November 6 th when the separation at 18:54 will be about one arcminute from our location – very close to being a grazing occultation. On December 27 th Venus is just over a degree from Neptune . Throughout the first half of the year Saturn and Mars move gradually closer together in the evening sky. By July 6 th they are about two degrees apart and on that evening form an attractive conjunction with the three day old Moon which may be seen just below them. The closest separation of the two planets (less than a degree) occurs a few nights later on July 10 th. The Moon is also in conjunction with Saturn on the evenings of January 24 th – 25 th, February 20 th, March 19 th, April 15 th, May 12 th and June 8 th and then in the morning sky on September 27 th, October 25 th, November 21 st and December 19 th. On the evening of August 13 th Venus and Saturn will be less than a quarter of a degree apart, but this will be another difficult event to observe, low on the western horizon at dusk. Venus then closes in on Mars and these two will be about a third of a degree apart in evening twilight on September 11 th. The Moon skirmished with the Pleiades twice in 2007 and there are two further encounters in 2008. The first of these occurs in the early hours of September 20 th when Celaeno (magnitude 5.4), Taygeta (4.3) and Maia (3.9) are all occulted. This event lasts between 1:53 and 3:17 . On the evening of November 13 th in an event lasting between 18:29 and 20:49 , the Moon occults Electra (3.7), Merope (4.2), Alcyone (2.9), Atlas (3.6) and Pleione (5.2). Minor Planets Many dozens of minor planets (asteroids) are within range of amateur instruments. The following are at opposition with magnitude 9 or brighter during 2008:-
1 Ceres, the largest asteroid and first to be discovered does not come to opposition during 2008 but is brighter than magnitude 9.5 at all times. Meteor Showers The following table shows the most important annual meteor showers with the dates of their expected duration during 2008, the date of maximum intensity, estimated zenithal hourly rate (ZHR) at maximum and the phase of the Moon at maximum. Those showers with the highest percentage for the lunar phase will experience the most interference from moonlight, consequently reducing the numbers of meteors observed.
Amongst the major showers, the Quadrantids in early January will suffer only a little interference from the last quarter Moon towards dawn, whilst the Perseids in August will be best observed at maximum after midnight , once the waning gibbous Moon has set. The Geminids in December will unfortunately be severely affected by the Full Moon. Sources The following are gratefully acknowledged:- Almanako.com, Burnham’s Celestial Handbook, Castle Point Astronomy Club, Graystel Astronomy Software, Heavens Above website, HM Nautical Almanac Office, International Meteor Organization, National Maritime Museum / Royal Observatory Greenwich, Royal Astronomical Society of New Zealand, US Naval Observatory. Appendices Appendix 1: Summary of Key Events in 2008
Appendix 2: The Messier Catalogue Note: Right Ascension (R. A.) and Declination co-ordinates are J2000 epoch.
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||