Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Angular Diameters of Compact Planetary Nebulae   We have obtained H$\alpha$ CCD images of 21 compact planetary nebulae in the
galactic bulge. All objects are resolved and, after deconvolving the seeing
disk, we find diameters of 1--2$''$ with typical uncertainties of 20\%. The
values are generally in good agreement with radio measurements but are smaller
than older optical measurements. Based on the new values, we find that the
Shklovsky method for distance determination greatly overestimates the actual
distance for all of our objects.

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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: cond-mat
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The categories of this paper are: atom-ph
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The categories of this paper are: math-ph
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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: ao-sci
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: adap-org