AUGUST  2013

AUGUST STAR MAP | MOON PHASE CALENDAR | STARWATCH INDEX | NIGHT SKY NOTEBOOK

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885    AUGUST 4, 2013:   Picnic with the Perseids

This is the best weekend of the year for people to gather for a picnic, and then to spend a few quality hours looking at the heavens. It is Perseid party time, and those bright streaks of light created by the dusty dross of Comet Swift-Tuttle sweeping into Earth’s atmosphere are sure to bring delight to anyone who cares to look into the night sky. The two best days for viewing occur on the mornings of August 12 and 13, a Monday and a Tuesday, when suburban rates before dawn could top 30 meteors per hour; but there will still be plenty of good observing on the weekend prior to the peak times. Just don’t believe the exaggerated hype of the media predicting rates of 100 meteors per hour. In suburban locales, a day or two before maximum, respectable rates are 10 meteors per hour before midnight and a little higher thereafter. One positive aspect of observing the Perseids before maximum is that they tend to appear somewhat brighter. Like all meteors which orbit the sun in an organized pack, they will appear to diverge from a radiant, a specific area of the sky, making their identification a snap. Begin your star party around 10 p.m. with lawn chairs facing towards the NW. Since the sky is normally darkest at the zenith, lay back and look overhead. Perseid meteors will seem to diverge upward from the NE. They will be swift, and some of them will leave luminescent glows that will persist for an instant to many seconds. As the night progresses, face your chairs more to the east, but keep looking overhead. Most of the meteors will still appear to radiate upward, but you’ll also begin to catch Perseids glinting below the radiant point which will help to increase numbers. In the predawn hour, weekend rates could top as many as 20 meteors as the radiant reaches skyward toward the zenith. Don’t worry about the moon; it sets before midnight through maximum night. Good eating and good observing!

Perseid meteors will appear to radiate from the area marked “X” on the map. Face lawn chairs towards the NE around midnight, east after 3 a.m. Observe the area of the sky around the zenith because that region is almost always the darkest. Meteor rates from suburbia could top 20 event per hour over the weekend of August 10-11 and about 30 shooting stars per hour on the mornings of August 12-13. After the morning of August 13 meteor rates decline rapidly. The best rates will occur about one hour before dawn. Gary A. Becker map composed with Software Bisque's, The Sky...

886    AUGUST 11, 2013:   Secrets of Copernicus

One of the great controversies about the moon prior to and during the Apollo program involved whether lunar craters were created through meteoritic impact or volcanism. Ground zero for the debate was a large 60 mile in diameter crater named Copernicus located on the edge of the Imbrium Basin. Here, features supported by both arguments could be made, but in the end, the impact theorists won the day; Copernicus was created by a large meteorite, perhaps 10 miles in diameter, which walloped the moon 800 million years ago. This impact site will be unveiled on August 15 as the terminator, the boundary separating night and day, slowly sweeps past the crater. Observers using small telescopes can witness the debate itself. An online photo of Copernicus is available at astronomy.org. Copernicus was created by a meteorite, not the collapse of a giant volcano. Copernicus’ crater walls are terraced (stepped) showing that when the meteorite hit, the vibrations from impact cracked or faulted the crater walls. The ground collapsed along the fault zones creating the stepped features of Copernicus’ ramparts. In the center of Copernicus, central peaks (mountains) formed. Central peaks are considered to be rebound features similar to the upward splash that is caused when a rock is thrown into water. The impact occurred on a rocky surface and the “splash” became petrified in the lunar rock, forming numerous central mountains. Surrounding Copernicus are many sinuous channels that proponents of volcanism thought were areas where lava flowed. Impact supporters believed correctly that these arc-like features were formed from debris clumps thrown from the impact site. As the moon waxes into its full phase by week’s end, Copernicus will display a brighter, prominent ray pattern created by the gardening of the soil from material ejected from the crater after the impact.

Copernicus is one of the great craters on the lunar surface. Locate it, center left, on the image near the terminator which separates day from night. Many of the features noted in the above article can be seen in this digital photo. The arc-like patterns created by great clumps of debris thrown from the crater are not seen, but the central peaks, crater wall terracing, and the ray pattern surrounding Copernicus are visible. The rays will become more prominent during the week surrounding full moon. Gary A. Becker image taken with a Questar 3.5-inch telescope from Coopersburg, PA…

887    AUGUST 18, 2013:   Astronomy All Over the Map

On the outbound trip to Hanksville, Utah and the Mars Desert Research Station, one of our travelers, Sarabeth Brockley, purchased an extraordinary book titled, All Over the Map by David Jouris, Ten Speed Press, 1994. According to its subtitle, it is an “extraordinary atlas of the United States, featuring towns that actually exist!” There are artistic, natural, divine, historical, eccentric, everyday, personal, and miscellaneous maps with real town names that defy description. Under the subheading of “Natural,” there is a heavenly map of the United States which hypes towns like Nova, Comet, Neptune, Aurora, Sunshine, Saturn, Seven Sisters, and dozens of other names which are astronomically slanted. We’ve all heard of Satellite Beach, Florida, near the Kennedy Space Center, but did you know that Florida also contains communities known as Jupiter, Venus, Sunrise, and Tropic? There is Half Moon, New York and Montana; and New Moon, Alabama; Moon, Oklahoma and Wisconsin; Luna and Los Luna, New Mexico; and Crescent, Oregon. And let’s not forget about the sun either! There is Sunset, California; Sun City, Arizona and Kansas; Rising Sun, Illinois; Sunshine, Arkansas and Maine; and Ray, Minnesota. There is also Sunrise, Florida, a retirement community, according to Jouris, which was originally named Sunset, but no retirees came to retire to it. Once the name was changed, the community began to sell. For more exotic astronomical town nomenclature, try Ozone, Tennessee; Pluto, West Virginia; Draco, North Carolina; Milky Way, Tennessee; Orion, Illinois; North Star Acres, North Dakota; and Polaris, Montana. There is also Terra, Utah; and Earth, Texas among many, many others. It is a wild and wacky world of town names in All Over the Map, and the astronomically identified cities and towns of the US are just the beginning.

888    AUGUST 25, 2013:   How Dark are your Clouds?

Clouds can tell you a lot about your observing location, whether it’s pristine, salvageable, or downright urban. One of my favorite stories regarding clouds occurred on the morning of July 11, 1991. It was barely dawn, and I was off the coast of Hawaii’s Big Island on the Independence, a cruise ship positioned on the centerline of a solar eclipse that was to take place some three hours later. I was out scouting a location on deck where the group I was hosting would be able to view the event as a unit and not be scattered all around the vessel. When I emerged on deck, the sky appeared nearly clear with a few slightly brighter insignificant patches where clouds were located. I was ecstatic because the forecast that I had seen the previous evening was grim with mostly cloudy conditions predicted for the Big Island. I was judging the sky like a “city slicker”—city lights cause clouds to appear brighter! That lasted about five minutes, until my eyes adjusted to the dimness, and features became more plainly visible. To my dismay, those few brighter patches that I had conjectured were flimsy cirrus, were actually little patches of clear sky against an almost overcast firmament. We saw the eclipse because the ship had a certain amount of maneuverability, and we were able to steer away from our nemesis; but over 50,000 eclipse chasers, stuck on the Big Island with no place to go, saw nothing except the clouds get even darker when the moon covered the sun completely around 7:30 a.m. The sky has a natural florescence, bright enough to allow clouds to appear darker against it from rural settings. In urban and suburban locales, this effect is unobservable because light pollution is reflected back from the clouds, causing them to appear brighter than the backdrop of the glowing sky. It is an easy enough observation to make to allow anyone to measure qualitatively the darkness of the nighttime sky.

A variety of lighting sources illuminate the sky from the Mars Desert Research Station near Hanksville, Utah. The pinkish cloud above the habitat glows from the lights of Hanksville, population 219, about five miles distant. The other clouds appear darker against the natural fluorescence of the sky created by high energy radiation and subatomic particles entering the Earth’s atmosphere. On either side of the image, yellowish light along the horizon delineates the location of distant thunderstorms. Good observing locations show darker clouds against a brighter sky background, while urban and suburban locales show brighter clouds against a darker sky. It is easy to obtain a quick qualitative assessment of your own observing haunts through this easy method. Gary A. Becker image from the MDRS, Hanksville, UT...