M75 by Rod Pommier

“Ever wish you could see some of the doubtless numerous deep sky splendors hidden from our view on the far side of our galaxy?

Well, here is one lying in plain sight. M75 is a globular cluster in Sagittarius lying at a distance of 67,500 light-years. This means when we view M75 we are peering past the southern side of the Milky Way’s core and seeing this globular cluster hovering above the far side of our galaxy’s disk. Harlow Shapley and Helen Sawyer classified globular clusters on a scale of I-XII based on how densely their cores were packed. Class I has cores so dense as to be virtually unresolvable, whereas Class XII are so loosely packed as to resemble circular open clusters. M75 is the only Class I globular in the Messier catalog and is notorious for having a core so densely packed that not even the largest amateur instruments can resolve it. However, the CDK 17 resolved its core spectacularly well.

Telescope/Mount: CDK 17 on L500 mount.

Camera: STL 11000M with Baader Planetarium LRGB filters.

Location: Pommier Observatory, Portland, OR, USA.

Exposures: L:R:G:B = 165:60:60:60 minutes = 5hours, 40 minutes total exposure at f/6.8