On the morning of 12 Sep at about 05.00 the shadows of both Ganymede and Callisto will be well visible on the planet's disc, and if you can follow the scene into the brightening twilight you'll see Ganymede enter into transit as well! The timetable will be (all times BST)
02.57: Ganymede Shadow Ingress
04.26: Callisto Shadow Ingress
05.58: Ganymede Ingress.
By 06.10 the sky will probably be too bright. Use a fairly high power to darken the sky background from about 05.30.
If you want to photograph the triple event, do so just as soon as Ganymede is mainly onto the disc, before the sky gets too bright. Also, the contrast between Ganymede and Jupiter itself is greatest when the satellite is silhouetted against the darker planet limb. As it progresses onto the brighter area of the disc, the contrast is lost.
Those in the W of the island will have the best view, as the Sun will be lower below the horizon at that critical stage.
You can find predictions for the times of all the satellite events on various websites, such as http://www.rasnz.org.nz/SolarSys/JovSatJul.htm.
More here: astromaster.astrolapalma.com"
14. The Elements in the Universe: Ulster Museum, 11 October, 12.00 - 4.30). this event will be looking at the Universe from an elemental point of view. Dr Mike Simms will be there with his meteorites. He has also invited IAA members to participate, particularly those with telescopes, especially if linked to spectroscopy of the Sun and stars. If anyone is interested in being involved, please contact Mike so that he can plan the event. firstname.lastname@example.org
16. COMET NEAR-MISS WITH MARS, Oct 19:
Comet Siding Spring will pass 134,000 kilometres from Mars on October 19. The neutral-gas coma of the comet, which extends for more than 100,000 kilometres in all directions from the nucleus, may well interact with the atmosphere of the planet. Ions may extend away than that, and the tail is millions of kilometres long. As a precaution, the orbits of the Martian orbiters have been altered to place them on the safe side of the planet during the most dangerous part of the encounter, which will occur when Mars' path through the comet's tail reaches the region of highest dust density, about 100 minutes after closest approach.
Nevertheless, every effort will be made to get good observations from the comet from all the spacecraft on or near the Red Planet. Siding Spring is a long-period comet on its first visit to the inner Solar System and spacecraft designed to study Mars up-close are not idea for good observations of the tiny comet nucleus much further away.
The comet's coma of dust and ice particles are the main hazard for the orbiters, but will not affect the rovers on the surface which will be protected by Mars' atmosphere. Even though it's much thinner than ours, the tiny particles in the coma will burn up without reaching the ground.
Each spacecraft will observe the comet as best as possible using its respective instruments. Most attention will be on the comet's coma -- its size, composition, the size of the particles, how it varies with time, and the jets from the nucleus. They will also study the comet's effect on the Martian atmosphere. And one spacecraft may possibly be able to image the tiny nucleus of the comet, only 1-2 kilometres across, as it passes by at the challenging relative speed of 57 km/s. But most instruments will be able to see the coma or the coma's effects on the atmosphere.
The spacecraft involved are: 1. Mars Reconnaissance Orbiter. Has 3 cameras plus an imaging spectrometer and a radar sounder. 2. Mars Express. Will use HRSC camera and ultraviolet/infrared atmospheric spectrometer. 3. Mars Odyssey. Will use THEMIS thermal emission imaging system. 4. MAVEN, arriving 2014. Has a suite of instruments devoted to Mars' upper atmosphere, but no camera. 5. Mars Orbiter Mission, arriving 2014. Has a varied instrument suite but not sure if it will be performing Siding Spring observations.
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