| Meteor Watching 101: Tips and terms By Robert Roy Britt Senior Science Writer posted: 30 June 2005 07:58 am |
Meteor Watching Tips
> The part of Earth where dawn is breaking is always at the leading edge of our planet's plunge along its orbital path around the Sun. This part of the planet tends to "catch" oncoming meteors left by a comet, whereas the other side of Earth, where it is dusk or late evening, outruns the debris. For that reason, the hours between midnight and dawn are typically the best time to watch a meteor shower. > Allow time for your eyes to adjust to darkness. A good hour is smart, so that you can also practice some prior to prime observing time. > Dress warmer than you think you need to, especially in winter. > Bring a lounge chair or blanket, so you can relax and look up with ease. > During meteor showers, shooting stars appear to emanate from a point in the sky called the radiant. There are different ideas about how to use this fact to aid in spotting meteors. Robert Lunsford has these thoughts: One idea is that it is preferable to look away from the radiant so that the shower meteors you see will be longer and therefore easy to detect motion. As Mark Davis stated one should look 20-40 degrees distant. At this distance the radiant is still in your field of view so that shower association is still fairly easy. Those who look directly at the radiant can see shower activity travel in any direction. Shower association will be fairly obvious. Meteors that appear near the radiant will be foreshortened and therefore the motion will be more difficult to detect. I would suggest that new observers face slightly away from the radiant. Those who enjoy good perception over a large field of view may be able to directly face the radiant with no problems. Those who prefer to face the radiant must not do so unless the radiant is at least 50 degrees high in the sky. If you don't then you are wasting the bottom portion of your field of view on the ground! |
Full coverage: Leonids Special Report
Glossary of meteor terms
SOURCE FOR GLOSSARY:
International Meteor Organization
Fireball: A bright meteor with an apparent visual magnitude of -4 mag. or brighter.
Limiting Magnitude: Generally denotes the faintest star visible during an observation and evaluates the quality of the sky as well as the observing technique. The magnitude of the faintest meteor visible can be different from the stellar limiting magnitude, particularly for photographic and video observations. Visual observations assume about the same limiting magnitudes for stars and meteors.
Magnitude: The brightness of stars and other celestial objects. Smaller numbers are brighter (negative numbers are the brightest). The scale assumes dark skies. Venus is -4.4, and the faintest star visible to the naked eye is about +6.0.
Meteor: The light phenomenon which results from the entry into the Earth's atmosphere of a solid particle from space.
Meteorite: A natural object of extraterrestrial origin (meteoroid) that survives passage through the atmosphere and hits the ground.
Meteoroid: A solid object moving in interplanetary space, of a size considerably smaller than a asteroid and considerably larger than an atom or molecule.
Meteoroid Stream: Stream of solid particles released from a parent body such as a comet or asteroid, moving on similar orbits. Various ejection directions and velocities for individual meteoroids cause the width of a stream and the gradual distribution of meteoroids over the entire average orbit.
Meteor Shower: A number of meteors with approximately parallel trajectories. The meteors belonging to one shower appear to emanate from their radiant.
Micrometeorite: A small extraterrestrial particle that has survived entry into the Earth's atmosphere. The actual size is not rigorously constrained but is operationally defined by the collection procedure. Micrometeorites found on the Earth's surface are smaller than 1mm, those collected in the Stratosphere are rarely as large as 50 micro-m.
Radiant: The point in the sky where meteors from a specific shower seem to come from. (Technically: The point where the backward projection of the meteor trajectory intersects the celestial sphere.)
Sporadic Meteors: Those not associated with a particular meteor shower.
UT, or Universal Time, is 5 hours ahead of Eastern Standard Time, and 4 hours ahead of the East Coast during Daylight Savings Time. UT is the same as Greenwich Mean Time (GMT), the 0 hour beginning at Greenwich mean midnight.
Zenith: The point in celestial sphere directly overhead from an observer.
ZHR (Zenith Hourly Rate): The number of shower meteors per hour one observer would see if his limiting magnitude is 6.5 magnitude and the radiant is in his zenith.
SOURCE FOR GLOSSARY: International Meteor Organization
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