Astrometric quality of the USNO CCD Astrograph (UCA)
نویسنده
چکیده
The USNO 8–inch astrograph has been equipped with a Kodak 1536x1024 pixel CCD since June 1995, operating in a 570–650 nm bandpass. With 3–minute exposures well exposed images are obtained in the magnitude range R ≈ 8.5 − 13.5. An astrometric precision of 10 to 15 mas for those stars is estimated from frame–to–frame comparisons. External comparisons reveal an accuracy of about 15 mas for those stars in a 20’ field of view. For fainter stars, the error budget is dominated by the S/N ratio, reaching ≈ 100 mas at R = 16 under good observing conditions. Subject headings: CCD astrometry, astrograph
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