Well, I decide to buy and try the Canon 100mm F2.8 macro lens. I already love the macro capability, It's fantastic and provides plenty of working room.
For astro, I gave it a go last night pointed at Sagitarius. Far from ideal conditions with plenty of light pollution, no light poluttion filter (damn, knew I should have got the in camera LPS filter
), and a near full moon just 45 deg away.
I over-did it.
Ran 6 shots at 200s at one stop from max, so F3.2 and ISO of 400. Same for darks. Processed an combined in IP and touched up in Photoshop. The images were seriously over-exposed and sky fogged, but here's the touched up stack for what it's worth.
Not really a fair situation to test the lenses capabilities, but I certainly found it easy enough to get a sharp focus.
Really need to try it out under darker skies. Anyway, whether it works out to be a gem for astro or not I'm already very happy with it's terrestrial capability - great portrait lense too