After overcoming the deficiencies of previous image-processing techniques, a novel technique based on the edge-detection of Saturnian ring is developed to precisely measure Saturn’s position. Furthermore, the scatter...After overcoming the deficiencies of previous image-processing techniques, a novel technique based on the edge-detection of Saturnian ring is developed to precisely measure Saturn’s position. Furthermore, the scattering light (i.e. halo light) of Saturn and its ring is removed effectively based on its center symmetry. Therefore, we have much more opportunities to accurately measure the positions of Mimas and Enceladus—two satellites very close to the Saturn. Experimental tests with 127 frames of CCD images obtained on the 1-meter telescope at the Yunnan Obeservatory over three nights show that the geometric center of the Saturnian ring and its 4 satellites (Tethys, Dione, Rhea and Titan) have the same positional precision, and the standard error for a single observation is less than ±0.05 arcsec. It is believed that these new techniques would have important impetus to the positional measurement of both Saturn by using a CCD meridian instrument and its faint satellites by using a long focal length telescope.展开更多
The images of the open cluster NGC2168 are taken using the newly-fitted 2k×2k CCD attached to the 1-m telescope at the Yun-nan Observatory with two different orientations. After the catalogue position of a star f...The images of the open cluster NGC2168 are taken using the newly-fitted 2k×2k CCD attached to the 1-m telescope at the Yun-nan Observatory with two different orientations. After the catalogue position of a star from UCAC2 is compared with its corresponding measured position, a surprising result shows that a small field of view (about 7′×7′) exhibits an obvious distortion. Spe-cifically, the polynomial between the standard coordinate (ξ,η) and its corresponding measured one (x,y) for a star in each field of view has significant terms as high as 4th order. Accordingly, the positional measurement accuracy of a bright UCAC2 star can be derived as well as ~7 mas in each direction (60 s of exposure time and near the zenith). This new finding would be important for a CCD image to deliver a highly accurate position in its whole field of view.展开更多
基金the National Natural Science Foundation of China(Grant No.10273015)
文摘After overcoming the deficiencies of previous image-processing techniques, a novel technique based on the edge-detection of Saturnian ring is developed to precisely measure Saturn’s position. Furthermore, the scattering light (i.e. halo light) of Saturn and its ring is removed effectively based on its center symmetry. Therefore, we have much more opportunities to accurately measure the positions of Mimas and Enceladus—two satellites very close to the Saturn. Experimental tests with 127 frames of CCD images obtained on the 1-meter telescope at the Yunnan Obeservatory over three nights show that the geometric center of the Saturnian ring and its 4 satellites (Tethys, Dione, Rhea and Titan) have the same positional precision, and the standard error for a single observation is less than ±0.05 arcsec. It is believed that these new techniques would have important impetus to the positional measurement of both Saturn by using a CCD meridian instrument and its faint satellites by using a long focal length telescope.
基金supported by the National Natural Science Foundation of China and the Astronomical Joint Fund under the Chinese Academy of Sciences (Grant Nos. 10573008, 10778617, 10973007)
文摘The images of the open cluster NGC2168 are taken using the newly-fitted 2k×2k CCD attached to the 1-m telescope at the Yun-nan Observatory with two different orientations. After the catalogue position of a star from UCAC2 is compared with its corresponding measured position, a surprising result shows that a small field of view (about 7′×7′) exhibits an obvious distortion. Spe-cifically, the polynomial between the standard coordinate (ξ,η) and its corresponding measured one (x,y) for a star in each field of view has significant terms as high as 4th order. Accordingly, the positional measurement accuracy of a bright UCAC2 star can be derived as well as ~7 mas in each direction (60 s of exposure time and near the zenith). This new finding would be important for a CCD image to deliver a highly accurate position in its whole field of view.
