Harold Corwin

IC 809 = IC 3672 was first found by Lewis Swift on 6 May 1888. His position is good, and his description, "eF, pS, R; bet 2 sts; all 3 point to [NGC] 4621" is appropriate for the galaxy and the field around it. NGC 4621 (M59) is about 6.5 arcminutes to the south-southeast, well within Swift's 32-arcminute field.

Schwassmann was the next to publish a position and description for the galaxy and included it in his 1902 Virgo Cluster list as number 213. He has two positions for the galaxy, and the resultant mean position is close to the modern ones. The appearance on the plates ("vF, vS" and "F, S, R, li * 12") is consistent with Swift's visual impression.

Up to this point, the equality of the two objects probably would not have been questioned by Dreyer. However, Frost, in his examination of a Harvard plate of the Virgo area, has two objects listed here. He equates the northern of them with IC 809 and describes it as "vF, R, d 0.'1 (I.C. 809, Sw. VII)". The first problem here is the note "d[ouble] 0.'1" which the galaxy is not; no image I've seen has the object as a double galaxy. Is there perhaps a defect on Frost's plate? His second problem: his position is about 4 arcminutes north of Swift's, near VCC 1909. While it is just possible that he picked up the fainter galaxy, it is a 16th magnitude, low surface brightness dwarf, unlikely to show up on the early Harvard plate. This should be checked, of course, once the scans of these plates are available online.

Frost's second object is 4 arcminutes south of the northern. Frost makes it simply "bM, magn. 13 (Sch. 213)", and his position is close to Schwassmann's, so this may be the real image of IC 809.

My own hypothesis is that Frost's northern object, which he took to be IC 809, is actually a plate defect. This would account for its peculiar description. This, of course, can be checked with the original plate. In any case, Frost's southern object, which Dreyer took to be new, is clearly identical to Swift's nebula. So, the identity of IC 809 and IC 3672 is pretty well established.

― IC Notes by Harold Corwin

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