Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Visual Photometry: Colour and Brightness Spacing of Comparison Stars   A significant amount of data on the historical and current behaviour of
variable stars is derived from visual estimates of brightness using a set of
comparison stars. To make optimum use of this invaluable collection one must
understand the characteristics of visual photometry, which are significantly
different from those of electronic or photographic data. Here I show that the
dispersion of estimates among observers is very consistent at between 0.2 and
0.3 magnitudes and, surprisingly, has no apparent dependence on the colour of
comparison stars or on their spacing in brightness.

2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
16
The categories of this paper are: stat
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The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
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The categories of this paper are: q-alg
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The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con