So are we talking in terms of CCD imaging with this camera or as an electronic device for observing DSO's? Thank you!
I'm planning on initially using the A7S for astrophotography and nightscape photography, i.e.: imaging. Even with 30 sec exposures the A7R is more than capable of this; the A7S should be great!
I do plan to try astro-video with the camera. It has the potential to capture brighter stellar objects but not too sure about DSO's (deep sky objects)? The A7R with a fast lens (f/2.0) is the first DSLR I've owned that would capture reasonable real time video of the Aurora Borealis. If the A7S lives up to the marketing hype, it might just work in this capacity? If nothing else, capturing a few minutes of 30 fps 4K video might give me a few thousand frames of pretty reasonable images to align and stack. 7200 frames (2 minutes) would yield a signal-to-noise ratio improvement of 85x over that of a single frame; might just work??
I suspect real time astro-video with the A7S will require a good fast lens which due to the price of long fast lenses will probably limit me to, at most, wide-field astro-video... However, if you consider "real time" astro-video as being a sequence of frames/images displayed at 5-7 second intervals (i.e.: Mallincam style), I suspect the A7S will perform very well! The A7R is almost at this level of performance with 30 sec exposures.