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Craig;

Is there any chance you would be willing to re-assemble the article and post it in the "articles"s section here?

Thanks;
Steve Coe

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You're really onto something here, because OB associations have been the most undersung of all the different types of deep-sky objects. And yet several (Orion, Sco-Cen, Lacerta OB1, Cepheus OB2, Perseus OB1) are unaided eye objects and about 3 dozen are good binocular targets. I had intended on filling this gap in the literature of amateur astronomy by zeroing in on associations in a 2nd edition of my "Binocular Astronomy", but that project has been delayed by the appearance of a bogus, unauthorized, and out-of-date 2nd edition of the book (as has been discussed in CN's "Binoculars" forum).

However, at the risk of sounding like I'm blowing my own horn, I can tell you that there is a great deal of information about stellar associations in my other book "Sky Vistas." In fact some 40 associations are discussed in detail in that book, and there is a chart showing their distribution among the spiral arms in the Sun's neighborhood of the Galaxy. About the only thing these discussions don't have that would have been in the descriptions of (in fact fewer) associations in an authorized 2nd edition of "Binoc Astro" are detailed lists of member stars.

"Sky Vistas" is kind of pricey if all you want is information on associations; but it is in a lot of college and university libraries, so perhaps you can get it through a interlibrary loan program.

Also, in the 1995 issue of "Astronomy" magazine I published an article on associations titled "Big Sky Deep Sky". It is an introduction to the astronomy of stellar associations discussing such matters as the types of stars and other objects in them, the life-history of associations, and their distribution in the Galaxy. Unfortunately the magazine cut the original second half of that aticle, which described individual associations and was intended for the observer. However, much of that practical observing information is now in "Sky Vistas."

Craig Crossen

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The neglect of OB associations as a class of object for amateur observation is probably more historical. For one thing, the realization of their existence is very recent in comparison with the history of the telescope. And the generally quite large angular size of associations, in addition to their generally more dispersed nature, doesn't lend them to the awfully small fields of view most often suffered in days of yore.

Today's wide angle eyepieces, RFTs and binoculars are a revolution when you consider the equipment our forebears had to work with.

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Then again, for those who want to go really "deep", there is the huge association (or more accurately, "star cloud") of NGC 206 in the Andromeda Galaxy. I have seen this one in my 100mm f/6 refractor, although it doesn't seem to get really easy to see until you get into the 8 to 10 inch aperture range. Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
Prairie Astronomy Club
http://www.prairieastronomyclub.org

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Then again, for those who want to go really "deep", there is the huge association (or more accurately, "star cloud") of NGC 206 in the Andromeda Galaxy. I have seen this one in my 100mm f/6 refractor, although it doesn't seem to get really easy to see until you get into the 8 to 10 inch aperture range. Clear skies to you.

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Austin Texas amateur Bill Tschumy's "Where is M13," is an almost free downloadable software program that depicts the position of many objects in relation to out galaxy, in three dimensions. It makes a great companion to "Sky Vistas."

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