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There will be a total lunar eclipse on the morning of the winter solstice, Dec 21st. It is very rare for an eclipse to happen on the winter solstice (the last time was in 1638); however, it is just coincidence. A total lunar eclipse happens when the Moon passes into the shadow of the Earth, and so it is cut off from direct sunlight. But because the Earth's atmosphere acts like a lens and bends some of the light from the Sun onto the Moon, the Moon never disappears completely. Instead, it often turns a reddish orange colour, although the colour can range from a deep red to a yellowish orange-brown. This is a result of dust and pollution high in the Earth's atmosphere, so a dark eclipse will indicate that our atmosphere is not too clean. Because this eclipse occurs just before sunrise in Ireland, the Moon will be getting lower in the NW part of the sky as the eclipse progresses, so you'll need a good clear view to the NW to see it properly. The moon starts to enter the umbra, or the main central part of the Earth's shadow at 06:32 when it will be 20° above the horizon in the NW. From this time onwards, the curved shadow of the Earth will creep slowly across the Moon's surface, until the moon is wholly immersed in the shadow, marking the start of 'totality'. This will start at 07:40, when the moon will be only 7° above the horizon. Mid-Eclipse is at 08:17, but the moon will pass above the centre of the Earth's shadow so the Southern edge should appear darker than the Northern edge. It will be only 3° above the NW horizon at this time. The Moon will have set by the time totality ends. Since the Sun will be just about to rise at the time of the eclipse, the dawn twilight will be brightening the sky, which may make it quite hard to see the later stages of the eclipse, especially when the Moon is low down. Viewers in the NW of Ireland will get the best view, since the Moon will be just a little higher up during the eclipse, and the sky will be a bit darker. But the next lunar eclipse in which mid-totality will be visible from Ireland will not be until 2015, so we should make the best of this one. NOTES: We don't get an eclipse of the Moon every month because the Moon's orbit is tilted at an angle of about 5.5 degrees to that of the Earth. An eclipse of the moon happens only if Full Moon occurs at one of the two points where the two inclined orbits intersect. For the same reason, we don't get an eclipse of the Sun at every New Moon, but luckily there will in fact be an eclipse of the Sun at the following New Moon, on January 4. More on that later. No optical aid will be needed to see the eclipse, but binoculars will give a nice view of the earlier stages. Because of the decreasing altitude of the Moon, and the ever-brightening morning twilight, the best view of totality will be just after it starts, at around 07.45. Locations in the Greater Belfast Area which should give a good view of the whole eclipse would include the Craigantlet Hills, or any of the high ground to the west and north of the Divis/Black Mountain/Cave Hill range, with views over the N end of Lough Neagh. In addition, there may be a chance with this eclipse to observe a phenomenon called a Selenelion. This occurs when the sun and the eclipsed moon can be observed at the same time. This can only happen just before sunset or just after sunrise, and both bodies will appear just above the horizon at nearly opposite points in the sky. This arrangement has led to the phenomenon being referred to as a horizontal eclipse. More information on this and other astronomical events is on the IAA website: www.irishastro.org The Irish Astronomical Association's New Year Party will be held as usual in the Tudor Cinema, Drumhirk, Comber on Saturday 8th January 2011. A buffet meal will be available in McBride's, The Square, Comber. Food will be served at 6.00pm, but it is advisable to be there at 5.30pm. After the meal, members and guests will then make their way to the nearby Tudor Cinema for the feature film IRON MAN starting at 7.30pm and followed by a prize quiz. Free light refreshments will be available at the cinema, including Terry Moseley's famous hot punch. N.B. Due to seating capacity restrictions at the Tudor Cinema, numbers will be limited to 60, so early booking is advisable. BOOKING FORM Name …………………………………………………………………………… Address ………………………………………………………………………… E-mail …………………………………………………………………… Contact phone number ………………………………………………… Number of adults @ £12 per person ………… Number of children under 12 years @ £6 ………… Total amount submitted £…………… Payment is by sterling cheque, payable to The Irish Astronomical Association, or cash. The booking form and remittance must reach the IAA Treasurer's assistant: Mrs Josephine Magill, 5 Fairhill Road, Newtownabbey, BT36 6LY, no later than 20th December 2010. Money will be refunded only if the event is cancelled due to circumstances beyond our control. N.B. Please note that tickets will not be issued. Admission is guaranteed on receipt of this booking form and remittance.
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Pomrčina Mjeseca 21.02.2008. U četvrtak, 21. veljače 2008. rano ujutro, očekuje nas pomrčina Mjeseca. Mjesec u sjenu počinje ulaziti u 02:42h, a iz sjene izlazi u 06:09h. Središnji dio pomrčine, prolazak Mjeseca kroz sjenu, trajati će 58 minuta. Cijelu pomrčinu Mjeseca moći će otpratiti stanovnici Europe, Afrike, Sjeverne i Južne Amerike. Nakon ove, slijedeća će pomrčina Mjeseca biti vidljiva iz Hrvatske 16. kolovoza 2008, no Mjesec će te noći samo djelomično ući u Zemljinu sjenu, tj. neće biti potpuna već djelomična pomrčina Mjeseca. Tablicu sa ostalim pomrčinama Mjeseca možete naći u našem članku o pomrčinama. Pomrčina počinje u 01:34, ulaskom Mjeseca u Zemljinu polusjenu (P1). Mjesec će se u vrijeme ulaska u polusjenu nalaziti na jugozapadu. Ulazak mjeseca u polusjenu je vrlo teško uočiti, jer Mjesec još uvijek prima svjetlo direktno od Sunca. Polusjena se još naziva penumbra. Mjesec počinje ulaziti u Zemljinu sjenu (U1), u 02:42h, a u 04:00h već je cijeli Mjesec u zemljinoj sjeni (U2). Značajnije zatamnjenje će se moći primijetiti tek neposredno pred prvi kontakt Mjeseca sa sjenom (U1), kada će dio Mjeseca koji ulazi u sjenu postati značajno tamniji od ostatka Mjeseca. Sjena se još naziva umbra. Mjesec je najdublje u sjeni u 04:26h (maksimum), a iz sjene počinje izlaziti u 04:51h (U3). U 06:09h Mjesec će potpuno izaći iz sjene (U4). Pomrčina završava u 07:17h kada Mjesec potpuno izlazi iz polusjene (P4) iako taj dio pomrčine neće biti vidljiv iz Hrvatske, jer Mjesec pada ispod horizonta u 06:49. Tijekom potpune pomrčine, Mjesec nikada ne pada u potpuni mrak, već poprima crvenkastu boju. Ova je pojava posljedica loma svjetlosti u Zemljinoj atmosferi koja najviše raspršuje plavu svjetlost (zbog čega je nebo danju plavo), a najmanje crvenu. Crvena svjetlost koja se ne rasprši potpuno u atmosferi nastavlja (nakon loma) svoj put prema Mjesecu i čini ga crvenim. Boja koju Mjesec može poprimiti kreće se od narančaste, preko krvavo crvene, pa sve do tamno smeđe ili tamno sive, a ovisi o tome koliko je Mjesec duboko u Zemljinoj sjeni te o uvjetima u Zemljinoj atmosferi. Najcrvenije su pomrčine Mjeseca koje se dogode nakon velikih erupcija vulkana, kada velika količina prašine u atmosferi potpuno oboji Mjesec u crveno. Kako će neki dijelovi Mjeseca biti dublje, a neki pliće u zemljinoj sjeni, tako će i različiti dijelovi Mjeseca poprimiti različitu boju.