Harold Corwin

IC 1227 = NGC 6206. The identity was first suggested by Bigourdan himself in an italicized note in his big table. He puts the note under his second observation (1891) of the galaxy: "This nebula has in its neighborhood four stars, while Swift notes only three near NGC 6206, so I had thought at first that the two objects were distinct; but today it seems probable that NGC 6206 and Bigourdan 210 are identical."

Indeed they are. Swift's RA is 20 seconds of time off. This misled Bigourdan to a faint star coincidentally close to the three stars that Swift mentions in his description: "pF, eS, R, stellar; 3 vF sts nr n point to it." In his first observation of "NGC 6206", Bigourdan carefully notes the distances and position angles of the same three stars -- but the object that he took to be NGC 6206 is actually a fourth star that Swift apparently did not see (is it variable?).

Bigourdan realized his mistake in 1891. By the time he returned to the field for a final measurement of the galaxy (in 1895), his description for NGC 6206 is that of a single star, and he does not bother to make a third measurement of it. However, he does make four more measurements of his "new" nebula.

Altogether, he has ten measurements of the galaxy. The average of the ten positions falls within two arcsec of the modern position.

― IC Notes by Harold Corwin

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