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FROM: http://www.nightskyinfo.com Mercury Mercury shines at magnitude 1.5 and is visible in the west-southwest half an hour after sunset, about 10 degrees to the lower right of Venus. The planet lies in Aquarius, but the dim stars of that constellation will not be visible against the bright twilight sky. Telescopic observers may be able to locate Mercury during the daytime, but care is required. A moment's carelessness may put the Sun in the field and ruin your eyesight. Choose a day when the sky is very clear and either use setting circles or just press "GO TO" if your telescope is permanently set up and has this facility. Mercury is 20 percent illuminated and at only 9 arcseconds diameter is probably best observed using a webcam attached to your telescope. Finder map - 45 minutes after sunset, looking west-southwest. Venus Appearing as a brilliant star-like object, our sister planet adorns the evening sky low above the west-southwest horizon about 30 minutes after sundown. The planet is now virtually full (90-percent sunlit), and through a telescope displays a tiny disk 11 arcseconds across. For such a dazzling naked eye sight, Venus is one of the most profoundly disappointing sights in the telescope. The planet's surface is perpetually obscured by an extremely thick atmosphere, so any observations will be limited to details discernible in its rather bland covering - slightly brighter or darker areas, or irregularities in the terminator. It has been found that the top of the atmosphere lies around 250 miles above the surface, and that the upper clouds have a rotation period of only 4 days. The upper clouds lie at an altitude of 45 miles, and there are several definite cloud-layers, though below 20 miles the atmosphere is relatively clear and calm. The atmosphere's main constituent is carbon dioxide, accounting for over 95 percent of the whole; most of the rest is nitrogen. The clouds are rich in sulfuric acid; at some levels there must be sulfuric acid "rain" which evaporates before reaching ground level. Mars Mars is visible in the morning before sunrise, far lower left of bright Jupiter. It glows feebly at magnitude 1.4 but should be easy to spot with binoculars as long as you have an unobstructed southeastern horizon. Mars is also known as the Red Planet, although its true color varies from rusty orange to gray. Some casual earthbound observers mistake it for a red-giant star, however, because of its significant apparent diameter it does not twinkle as a star does. In ancient times, the planet's wandering motion and blood-red color were portents of ill tidings, and this led the Romans to name Mars after their war god. Yet the source of the reddish hue is not the bloody spirit of the Roman god, but simple iron ore. The Martian surface contains large amounts of iron oxide, red and rusting. As Viking 1 and Mars Pathfinder images revealed, even the Martian sky takes on a rust-pink tinge during seasonal dust storms. The dust is blown from the surface by winds with speeds exceeding 150 to 300 feet per second, and forced into the atmosphere, where it remains suspended for weeks. Widespread dust storms are commonest when Mars is near perihelion (the point in its orbit when it is nearest to the Sun), and the surface winds are at their strongest. Jupiter Jupiter is a bright precursor of the Sun, visible high above the southeastern horizon at dawn's early light. The planet shines at magnitude -2 and through a telescope displays a disk slightly more than 30 arcseconds in diameter. While Mercury, Venus, and Mars are difficult and sometimes frustrating objects to observe with amateur telescopes, the largest of the planets, Jupiter, is a very different prospect. Even the smallest telescope or 10x80 binoculars mounted on a tripod will resolve the planet's disk, and show it to be crossed by horizontal dark belts. The Great Red Spot is also clearly visible, and the use of a blue filter will enhance the contrast for its observation and for that of other cloudy structures of Jupiter. The dance of the four main satellites is also very striking. They provide a never-ending fascination for amateur astronomers. Io, Europa, Ganymede, and Callisto (in order of increasing average distance from the planet) orbit the Jovian disk, sometimes occulted, sometimes projecting a tiny shadow when they pass between Jupiter and the observer. Saturn Saturn grows to prominence in the east within an hour or so after it rises (it breaks the horizon around 6 P.M. local time) and is well up in good telescopic view by 10 P.M. local time. The planet gleams at magnitude 0.1 and its elegant rings span 46 arcseconds. Saturn is the telescopic showpiece of the night sky, and the chilling beauty of the small pale orb never fails to elicit a gasp when people see it for the first time. Any telescope magnifying more that 30x will show the rings, and the view is exquisite in 6- to 8-inch instruments. All four gas giants are surrounded by a ring system, but Saturn's is the most extensive and spectacular. The broad, but thin, system appears to be divided into several wide rings, but each of these consists of thousands of separate narrow ringlets. Each ringlet is made of billions of particles - largely water ice - that range in size from microscopic specks to mountains several miles across. The rings are not as old as the planet. They are thought to be only a few hundred million years old and are the remains of an icy satellite which wandered too close to Saturn and paid the supreme penalty.
Uranus Uranus is lost in the evening twilight, setting soon after the Sun. It will return to view in early May, low in the morning sky.
Neptune Neptune is too deep in the solar glare and cannot be observed until early April, when it will reappear in the morning sky.
Pluto Pluto is barely emerging from the glow of dawn, so it will be obscured for many observers. It will not be high enough above the horizon for telescopic viewing until later this month.
Asteroids
Anyone who turns binoculars to the winter sky is bound to have a look at M44, an open star cluster which lies at the heart of the small constellation Cancer the Crab. This group appears as a misty cloud to the unaided eye under a dark sky, but resolves into a few dozen sparkling stars with the smallest optical aid. Asteroid 20 Massalia shares the same binocular field with M44, but you will really need a telescope to track down the 9th-magnitude space rock. To navigate with the finder map below to the exact position of Massalia, you need to compare it to what you see. The first thing you must know is your finderscope's field (a typical finder shows a view about 5 degrees wide). Check by aiming at a star within about 10 degrees of the celestial equator, and turn off the clock drive if any. Center the star, then time how many seconds it takes to drift to the edge. The number of seconds divided by 2 is the field diameter in arcminutes. On star charts north is up and east is left. When peering into the eyepiece, find north by nudging the telescope slightly towards Polaris - new stars enter the field from the north edge. Turn the map around and hold it so north on the map matches this direction. Lastly, make sure your telescope gives a correct image rather than a mirror-image; this may mean removing a right-angle star diagonal at the eyepiece. A mirror-image view is nearly impossible to navigate in using a correct-image map. If you do observe with a mirror-image, you can import the map into an image-processing program, flip the image right-for-left, and print it out; this will match your view. |