Star Points for August, 1997 (REVISED); by Curtis Roelle Swift Mercury and Crippled Mir Visible in Early Evening Last month we discussed Earth's "twin sister" planet Venus currently shining proudly and brightly as an "evening star" in the western sky after sunset each night this Summer. (Of course Venus is a planet, not a star.) Sky watchers who get themselves outside early -- early in the month and early in the evening -- get an extra bonus: Mercury, our solar system's innermost planet, has been visible the first week of this month. You may still have time to get a glimpse. (Alas, this column appears one week late due to inadequate column space last Friday and in the meantime Mercury has started sneaking off!) Begin your Mercury observation by finding Venus about 30 minutes after sunset, or just after 8:30 p.m. EDT. Facing west you'll see a bright star-like object 10 degrees above the horizon. This is roughly the width of your fist outstretched at arm's length and applies to all persons regardless of size or age. Venus is easily seen with the unaided eye and appears brilliant and star- like. Mercury will is to the right and below Venus, about halfway to the horizon. Binoculars will be a big help as will a horizon free of summer hazes. In some wide-field binoculars both Venus and Mercury fit into the same field of view. If the sky is exceptionally clear Mercury might be spotted with your unaided eye. Brilliant Venus appears nearly 50 times brighter than Mercury! In the sky Mercury reached greatest separation from the Sun on August 4. Astronomers call this position greatest eastern elongation". Western elongation occurs when Mercury achieves maximum separation from the Sun in the morning sky. The next western (morning) elongation will be on September 16. Mercury was named by the ancients for the messenger of the Greek gods. In mythology Mercury was swift of foot, a trait shared by the rapidly-moving planet. Mercury requires just 88 days to circle the Sun, the shortest orbital period of the nine planets. When the Mariner 10 spacecraft visited Mercury in 1974 it found a battered Moon-like world marked with numerous impact craters, without an atmosphere. Yet because of its proximity to the Sun the daytime surface temperature of Mercury reaches 770 degrees Fahrenheit, compared to "just" 220 degrees on the Moon. Another sight for Carroll County sky watchers are artificial satellites such as the Russian Mir space station. Mir has been plagued by difficulties in recent weeks including a fire, collision with a cargo spacecraft, and a power blackout. Mir currently has a crew of three including one American astronaut. One of the brightest and easiest to see satellites, Mir rivals Venus in brilliance. It appears as a slowly moving light climbing higher in the sky as it draws closer to the observer. Unlike an airplane there are no blinking or colored lights. Mir's light is steady, its color the yellowish-white of reflected sunlight. Two good opportunities for Carroll County residents to see Mir occur in mid-August. On August 16 Mir passes from northwest to northeast between 9:38 and 9:43 p.m. EDT, reaching more than halfway up the sky before disappearing into Earth's shadow. On August 18 Mir floats from northwest to southeast between 9:19 and 9:25 p.m. EDT, reaching a maximum altitude of more than 70 degrees overhead. (These times should be accurate to within five minutes unless Mir alters its orbit.) On the Web the "Birdwatch" homepage at provides information to satellite watchers in central Maryland. Birdwatch has observing schedules for selected NASA and DoD satellites as well as tutorial information and illustrations. It also has links to Web sites associated with the satellites it tracks and to repositories where you may download software and data for figuring out when and where your favorite satellite will be visible. I am interested in hearing your results, positive or negative, in viewing either Mercury or Mir. You can write to this newspaper or direct your e-mail to roelle@erols.com.