Minor Planet (4) Vesta
The bright object at the center of the images* is the Minor Planet "(4) Vesta". Vesta is the 4th asteroid discovered. It orbits the Sun at a distance of about 186 million miles and is approximately 300 miles in diameter. It is the 3rd largest asteroid in the main asteroid belt which lies between Mars and Jupiter. When the images above were taken from the JAT Observatory (Dec. 19 2005) the asteroid was near the constellation of Gemini and had a magnitude of 6.67, making it visible to the naked eye. Vesta is a slow moving object. It has a orbit of 3.6 years and moves about 3.3 arc seconds per hour. Some people believe a meteor that fell to Earth in 1960 near Millbillillie, Western Australia might be a piece of Vesta.
To see a really short time lapse image* on YouTube of the asteroid's movement click on either image above. You can also download and display the sequence here.
How it was done:
The images were captured using a dual chip SBIG ST2000-XM CCD camera attached to a Stellarvue 4" refractor piggy-backed on a wedge mounted Meade 10" LX200GPS. The time lapse animation is composed of 29 separate exposures which are 3 minutes in duration. A five minute delay was inserted between each exposure. This sequence was chosen in order to capture the asteroid's motion without it appearing as just a big white streak across the image. Because of the asteroid's very slow movement the imaging took place over an 8 hour time period. During that time, because of the Earth's rotation, the background stars and the asteroid moved from one side of the sky to the other, relative to the observatory. This required that the telescope be able to accurately track the target.
The LX200GPS telescope provided the tracking platform. To keep the telescope pointed correctly, a guide star in the vicinity of the asteroid was selected. The scope was sent guiding commands by means of a computer and the CCD autoguider within the ST2000-XM in order to keep the scope pointed at the star. The autoguiding occurred continuously during the 8 hour session while the imaging part of the camera acquired the photos. A second CCD camera (a Meade DSI Pro) was connected to the 10" GPS so the asteroid's position could also be monitored in real-time.
At the end of the session the separate images were simply converted from their raw FITS imaging format into an animated GIF format, they were not post aligned, registered or processed. Toward the end of the sequence clouds can be seen rolling in as well as a streak from a passing satellite. The picture on the left is the 1st in the sequence, the one on the right is the last. Notice the small distance the asteroid moved in those 8 hours.
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*Still images and composite animation are copyright protected and property of the JAT Observatory. They may not be used or reproduced in any manner without permission.
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