The central part of the nebula near Pismis 24 is very bright and I managed to get some fairly good resolution in that area so I made this comparison with images from La Silla and the Hubble Space Telescope. Interestingly, this image taken with a 10" telescope is really not much behind the ESO La Silla image that was taken with the Danish 1.5 metre telescope. The Hubble view is of course another story, but a fun comparison still.

The intense ultraviolet radiation from these stars is slowly eroding the surrounding gas and dust away and shaping the delicate structures visible throughout the region. The heaviest of these stars, designated Pismis 24-1, was long thought to weigh some 200 to 300 solar masses, well in excess of the theoretical upper mass limit of about 150 solar masses for an individual star.
But in 2006 high-resolution images taken with the Hubble Space Telescope showed that Pismis 24-1 is really two stars orbiting one another. Further to this, ground-based spectroscopic studies have revealed one of the stars to be a tight binary. Still, these three stars are among the heaviest known.

The cluster and nebula lies 8000 light years away in the constellation Scorpius.

Click here to see a wider view of NGC 6357 and Pismis 24.

Image details:
Date: 7th, 8th, 10th and 17th July 2012
Exposure: LRGB: 340:50:42:46m, total 7hrs 58mins @ -30C
Telescope: 10" Serrurier Truss Newtonian f/5
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2
Taken from my observatory in Auckland, New Zealand