I’ve found that some globular clusters don’t have a Shapley-Sawyer Concentration Class number. I know of two that are so bright that I’ve been able to see them in my 8x56 binoculars – NGC 6355 and NGC 6558. William Harris told me that it’s true those were never classified by Shapley/Sawyer and that the reason might have been because “They are in the Galactic bulge region, not very luminous, and obscured by quite a bit of foreground dust absorption.” Though that sounds reasonable, it still doesn’t quite answer it for me.
So I’m wondering if anyone has taken a stab at rating them? Late last year a friend bought me a copy of the Astronomical League’s Globular Cluster Guide and they show a way to determine that for yourself. So I’m thinking people have tried it and before I go and do it myself this summer, I’d like to hear what others have gotten!
Edited by SNH, 10 July 2020 - 04:46 PM.