Harold Corwin

IC 3636 is a double star. Earlier, I had suggested that is perhaps a triple; the fainter star looks like a blended double star on the DSS1. However, on the DSS2 and SDSS images, that star is clearly a single.

It was found on a plate taken by Max Wolf with the 16-inch Bruce refractor at Heidelberg on 27 January 1904. He published this and 197 other objects as new nebulae in 1905, and Dreyer incorporated most of them into the second IC. Wolf also measured positions for six NGC and IC1 objects on the plate.

As with most of the other plates in this series, we have been fortunate to be able to compare prints of them -- kindly made available to us by Dr. G. Klare at Heidelberg -- with the POSS1 and with the DSS. This plate, and two of the four others, still carry Wolf's original ink marks identifying the objects which he catalogued. This has made possible the positive identification of almost all of Wolf's objects on this plate which were included in the IC.

By the time Wolf examined this plate, he had clearly refined his techniques considerably over his first paper of new "nebulae," where most of the objects are in fact faint stars. Here, only 55 stars or defects are included as nebulae -- still a relatively high percentage, but not too bad considering that Wolf was working with images near the limit of the plate (about 18th magnitude).

― IC Notes by Harold Corwin

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