Open clusters?

[bomberbaz]

21 minutes ago, paulastro said:

I thought an asterism by definition consists of stars that are not physically related, but I could be wrong Stu.

I can think of several Clusters which have bright stars within their boundaries which are not physically related, but just happen to be in the line of site. 

If I remember correctly, in NGC 457 (the Owl or ET cluster) the two bright stars which are the 'eyes' are not actually part of the cluster.

 

I still say it looks like a bat but thats just me. 

[paulastro]

9 minutes ago, Stu said:

From what I can see, it is just any shape or pattern of stars which isn’t a constellation. Could be a smaller part such as the Plough, or could be parts of multiple constellations like the Summer Triangle. I think it can be both physically related stars and those that are not.

Thanks Stu.  I'm confused now  😁.  Though off hand, and it is late, I can't think of a star cluster  (with physically associated stars) which anyone calls an asterism?  Just out of interest, I googled star cluster, which came up with the definition below, though I'm not sure it actually helps us or not 😆. 

Anyway, everyone knows what the Pleiades looks like, whatever anyone  classifies it as 😊.