H-alpha filaments selection
Date, from:
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January
February
March
April
May
June
July
August
September
October
November
December
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
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1951
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1954
1955
1956
to:
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11
12
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14
15
16
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18
19
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21
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25
26
27
28
29
30
31
January
February
March
April
May
June
July
August
September
October
November
December
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
Heliographic longitude, from:
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Latitude, from:
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Area, from:
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Intensity, from:
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