StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

MAY 2001

MAY STAR MAP | INDEX | MOON PHASES

245 MAY 6, 2001: Planispheres: With the warmer weather of spring upon us and vacations beckoning, I’d like to suggest a handy little tool that will make your sojourns with the nighttime sky more enjoyable. The device is called a planisphere, and it is the most efficient way to take a personalized portrait of the heavens along with you on your travels. They are inexpensive, about $10.00 in a plastic version, and flat, so they pack well and are very space efficient. And most importantly, they work. An inner circle containing the hours of the day rotates around an outer circle which contains the days of the months. The view of the heavens is oval-shaped, showing the sky in all four directions. If you match the hour of the night with the day of the year, a correct representation the sky at that moment is achieved. To use a planisphere, simply look down upon it, holding the direction in which you are viewing closest to you. The sky in front of you will be depicted on the Planisphere quite accurately. Use a flashlight covered with red cellophane for illumination. Planispheres always give the standard time representation of the sky. Since we have jumped ahead one hour and are now on Eastern Daylight Time, subtract one hour on the planisphere to achieve the most accurate results. If it’s 11 p.m., EDT, set the planisphere time for 10 p.m. which would be the correct standard time. Planispheres are also designed for a specific latitude location which cannot be altered. So if you are planning a trip to Australia, a planisphere purchased at our latitude of 40 degrees north would be useless in Oz. Forget about planispheres with glow-in-the-dark stars. You’ll still need a flashlight. Purchase your planisphere at a local photo dealership.

246 MAY 13, 2001: Tracking the International Space Station: There is a wonderful web site which can be used to calculate the times of visibility for dozens of satellites including the International Space Station, the Space Shuttle, and the Hubble Space Telescope. It is a German site called Heavens-Above and it is appropriately located at www.heavens-above.com. Logging onto the site, you will immediately see a real-time map showing the location of the ISS. Its position is updated each time the page is refreshed. When I logged on, the ISS was over western Pennsylvania. Several minutes later, it passed nearly overhead as seen from Allentown. Unfortunately, it was 3:00 p.m., just my luck. You cannot see the ISS during the day. Finding the pertinent data for your specific town could not be easier. The web site houses data for over two million worldwide locations. Start by clicking on "Selecting from our huge data base," and this will take you to another page where your country can be found. Click on "U" and you’ll jump to countries that begin with that letter. Click on "USA" and enter the town or city in the appropriate box from which you will be making your observations. Allentown yields 16 possible locales across the United States, including Allentowns in Ohio, Mississippi, New Jersey, and two locations in New York State. Click on Allentown, PA and you are ready to discover when the International Space Station, Hubble Space Telescope, or dozens of other bright satellites are due to pass over the Lehigh Valley. You will find fly over times for the ISS for the next two weeks at today’s web version of this StarWatch article. Keep in mind that the orbit of the ISS often changes during Shuttle missions, so timely positional data is of the essence. Happy observing!
Fly overs of the International Space Station as seen from Allentown
247 MAY 20, 2001: Mars Returns: There is a strange new light becoming visible in the southeast if you’re an early morning stargazer. It’s bright and reddish, and it doesn’t twinkle like the stars. If you were alive on Halloween Eve 1938, this planet would have made a lasting impression upon you, for it was the backdrop of the most famous radio hoax in the history of broadcasting, War of the Worlds. The Red Planet is again on the attack, currently gaining prominence in the east after midnight. But now its canals and Martians are just a historical footnote, a part of Mars’ romantic past. As the weeks unfold into June, Mars will brighten and move westward in the opposite direction to its normal motion. This is an effect of a faster moving Earth catching up to Mars and passing it in just the same manner that a car or truck appears to travel backwards when you pass it on a highway. In astronomy this is called retrograde motion, and it will cause Mars to rise earlier than expected each evening. By early June, Mars will be visible low in the southeast at 11 p.m., but by mid-month, Mars’ presence in the sky will be easily noticed by late twilight. By mid-July, Mars will be in the south as soon as it’s dark and just slightly over five degrees from Antares, the brightest star of Scorpius, the Scorpion. Red Antares is Greek and means the rival of Aries. Aries was the Greek word for Mars, so the location of the Red Planet this summer next to Antares will be especially auspicious. Their location will be over the richest part of the Milky Way. However, Mars will dominate the scene, so observers will have an easy go at determining which objects are Mars and Antares. There will be more about Mars during June, or read ahead in the StarWatch section of the web address.

248 MAY 27, 2001: Moon Bright: There is something special about a full moon in the sky. Put some scudy, fast- moving clouds near it, a little chill in the air, and some distant lightning, and you have the setting for a hundred Hollywood horror flicks. The light of the full moon seems to tease the night into a deep twilight, revealing the landscape’s general features, but not that which lies within the shadows of our imagination. This week is a perfect time to watch the moon’s light burgeon from its first quarter phase which occurs on Tuesday to its full phase which takes place one week later. During this period you’ll watch the moon’s light increase by tenfold, as it moves into a position which is opposite to the sun. Check out the increasing brightness of the moon. You’ll notice distinct shadowing on the ground, and it’s fun to see where the shadows created by streetlights blend and are overpowered by the shadows being created by the moon. My grandfather used to reminisce about reading the newspaper by the light of the full moon when he was a soldier fighting in Russia during World War I. Keep in mind that this was during the winter with a snowcapped landscape. Try photographing the countryside under the light of the full moon. You’ll need a camera that can be controlled manually, a cable release, and a tripod. Try a fast film like Fujicolor 800 and take images in the range of F/2.8 to F/4.5, starting at 15 seconds. Continue doubling to 30s, 60s, 2 minutes, 4m, and there should be an acceptable photo within the lot. If the night is very clear, the sky will become a deep blue, and you will see stars also! See the author’s self-portrait taken under the light of a waxing crescent moon in today’s web version of this article.