Andrew Cooper
Jan 13, 2022    Lawa'i Beach, Kauai, Hawaii (map)
8x42mm Nikon Prostaff 3S Binoculars @ 8x
Seeing: 6 Transparency: 6 Moon: 0%

A bright coarse group 2° north of δ Vel, three 4-5th magnitude stars in a notable 30' triangle with a few fainter members within

Andrew Cooper
Jan 30, 2011    Hale Pohaku, HI (map)
46cm f/4.5 Newtonian, Deep Violet @ 60x
Seeing: 6 Transparency: 6.5 Moon: 0%

A coarse cluster of a few very bright stars in a 1° area

Andrew Cooper
Jan 13, 2008    Hale Pohaku, Mauna Kea, HI (map)
46cm f/4.5 Deep Violet

Very large, bright, sparse, poor, obvious naked eye object, a dozen bright stars in two clumps, decent in 12x36 binoculars, unimpressive in telescope

Harold Corwin

IC 2391. There is certainly a cluster here, and it was certainly rediscovered by Solon I. Bailey during his survey of the sky on Harvard Patrol Camera plates. However, it is still not clear, without delving into the professional literature, just which stars belong to the cluster, and which are in the field around it.

Bailey made the cluster only 15 arcmin across and centered it on Omicron Velorum. Brian Skiff and AH make it 60 arcmin across and still center it on the star, though on the DSS and the IIIaJ film, this larger cluster is clearly centered about 30 seconds of time to the east and 10 arcmin to the south (I call this "IC 2391 all" in the table). I put Bailey's 15 arcmin core about 10 seconds west and 2.5 arcmin south of Omicron.

For now, you have your choice. I'll do some digging someday and report here just which stars are cluster members and which are not.

In the meantime, AH have a fascinating Note relating this cluster's part in an all-sky stellar association, and Glyn Jones notes that the cluster was first recorded by al-Sufi.

― IC Notes by Harold Corwin

Drawings, descriptions, and CCD photos are copyright Andrew Cooper unless otherwise noted, no usage without permission.

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