Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Astrometric quality of the USNO CCD Astrograph (UCA)   The US Naval Observatory 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 $R
\approx 8.5 - 13.5^{m}$. 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
$\approx 100$ mas at $R=16^{m}$ under good observing conditions.

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The categories of this paper are: acc-phys
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The categories of this paper are: alg-geom
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The categories of this paper are: eess
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
1
The categories of this paper are: cs
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: patt-sol
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The categories of this paper are: math
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The categories of this paper are: physics
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The categories of this paper are: hep-th
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The categories of this paper are: atom-ph
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The categories of this paper are: supr-con
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc