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Дата изменения: Mon Feb 10 12:39:25 2003 Дата индексирования: Tue Oct 2 00:45:33 2012 Кодировка: Поисковые слова: europa |
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From: TerryMosel@aol.com Date: Sun, 9 Feb 2003 15:51:45 EST Subject: Last days of NEAT, MutJupSat Hi all, Comet NEAT is brightening & developing nicely, but is also plunging rapidly into the evening twilight. And the Moon is brightening.... So grab a look in the next day or two for the best views. I estimated it at magnitude 4 at 18.50 this evening, with a 2 degree tail, using 30x80 binocs. Prof Mark Bailey (Armagh Observatory) independently came up with exactly the same assessment, observing with 20x80s from Oxford Island (S Shore of Lough Neagh). Tolis Christou, observing from light-polluted Armagh thought it only slightly fainter. And John McConnell (Maghaberry) agreed on the magnitude, but saw only 1.5 dgrees of tail with 10x50s. It can be found for the next day or two by continuing the line down thru the diagonal of the Square of Perseus for its own length or a little more; after that the distance below the bottom corner of the Square increases rapidly as it nears perihelion. If you see it after St Valentine's day, at about magnitude 1-2, you'll be very lucky, unless it brightens much more than predicted! Mutual Jupiter satellite event tonight: At 00.51 on 10 Feb (or 24.51 tonight!), the innermost Jovian Moon, Io, will totally occult (or pass in front of) the second one, Europa. The total phase of the occultation lasts for only 9 secs, but the partial phases will obviously take longer. Unless you have a humongous telecope, and excellent seeing, you can't observe the detail of the event, but any small/medium sized instrument will show them approaching, merging, and then separating again. And you can observe the effect of the occultation by looking for the drop in brightness as Io cuts off the light from Europa. Just before the actual occultation starts you'll be seeing the combined light from both satellites: Io mag 5.0, and Europa, mag 5.3, give a combined mag of 4.4. During the total phase this will drop back to that of Io alone, i.e. 5.0. Try comparing the brightness with that of Ganymede, mag 4.6, the moon closest to the occulting pair. At the time of the occultation, the view from left to right in a normal inverted telescope image will be: Callisto, Ganymede, Io+Europa, Jupiter. At the time of writing the sky is 100% clear, so good luck! (I also saw the ISS, and two nice Iridium flares, earlier, so it could be a good night!) Terry Moseley
Last Revised: 2003 February 10th
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