Hi all,
this is my first attempt at the Antares/Rho Ophiuci complex. It was also the first real test of a recently acquired Pentax 6x7 165mm f2.8 lens.
I did previously attempt a couple of quick test pics with the lens wide open at f2.8 but found the CA around bright stars far too intrusive. This one is stopped down to f4 (hence the diffraction spikes) and although some CA remained it was reduced enough that I was able to remove most of it in processing. Unfortunately I wasn't able to keep much colour in most of the stars. Hopefully at f5.6 CA will be almost negligible so I'll try that next.
Ended up using just 4 x 4 min un-guided subs (each sub was actually 4 x 1 min using the camera's multi-exposure mode) through a Pentax K-5 DSLR (unmodded).
Somewhat larger version at Astrobin
http://www.astrobin.com/full/184790/0/