Austrian amateur astronomer Matthias Kronberger was a key member of the Deep Sky Hunters group that discovered numerous planetary nebulae. Here of some of the ones attributed to Matthias.

Click on each image for more details.
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Kn 9
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Kn 43 and Pa J1940.3+1855
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Kn 61
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Kn 131
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Kn 19
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Kn 45
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Kn 63
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Kn 24
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Kn 50
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Kn 121
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Kn 132
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Kn26
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Kn 59
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Kn 130