If you miss a faint asteroid at a favorable opposition, you may have to wait 4 or 5 years before you have another chance. The near-perihelion oppositions are called favorable. The retrograde motion slows gradually, and after approximately 45 days, the asteroid reaches a stationary point, after which it resumes its direct (West to East) motion.īecause of eccentricity, not all oppositions are equally good, If an opposition occurs when the asteroid is at aphelion (farthest from the Sun), the asteroid may be 2 or 3 magnitudes fainter than at perihelion (closest to the Sun). An asteroid at opposition reaches the highest point of its trajectory and crosses the local meridian about midnight.įor about 45 day's before and after opposition an asteroid appears to move in retrograde motion (East to West) against the background of the stars. An asteroid is at its brightest at opposition, so this is the best time to observe it. When the Earth catches up, the Sun, Earth, and asteroid are approximately in a straight line, and the asteroid is said to be at opposition. Because the Earth revolves around the Sun with a period of one year, it catches up with any particular asteroid approximately every 15 to 18 months. A few unusual asteroids have orbits that cross the orbit of Mars or the orbit of Earth. Their orbital planes are usually close to the orbital plane of Earth, but a few have inclinations of 20 degrees or more. Their orbits are usually elongated, with eccentricities between 0.05 and 0.35. Most main-belt asteroids have orbits with semi-major axes between 2.1 and 3.3 astronomical units and periods between 3 and 6 years. Most asteroid orbits lie between those of Mars and Jupiter and are called main-belt asteroids. Like planets, they revolve around the Sun. AsteroidsĪsteroids are also known as minor planets. Be sure to indicate which you prefer and provide the necessary address. After verification of your observations, your certificate (and pin) will be sent to you or your society's Awards Coordinator, whomever you specify. If you wish to have your copies returned, include a self-addressed stamped envelope. For the regular certificate (25 asteroids), submit copies of your sketches. To receive your certificate, send a copy (retain your originals) of your observations to the Asteroid Coordinator. To become a member of the Astronomical League as a Member-at-Large, contact the Executive Secretary. To qualify for an Asteroid Club award, you must be a member of the Astronomical League, either through an affiliated club or as a Member-at-Large, and you must observe and confirm the required number of asteroids. Hence an asteroid observing program can be carried out successfully from urban and suburban locations. Since asteroids appear as points of light rather than extended objects, they do not suffer from light pollution as much as deep sky objects.
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