I suspect that the limiter for us UK folk will be the presence of dark sky. This looks quite useful - a light pollution map. Some other useful links:

- Stellarium to see what you're looking at (website)
- Star Walk, my daugher's favourite app of mine. Point ipad at sky and it tells you what's there.

Worst lens I have. Seriously. Waste of space.

Works fine with K5, I'm on latest version

Yeah it's pretty impressive. I can't wait to use it. I have the camera primed on a tripod set up with some extra eq to help get great focus all ready and waiting, now to wait for some clear skies.

No, I can tell you it doesn't depend on where you're aiming, the max length it allows you depends on the mm of the lens, the unit gives you a maximum time available which differs per lens. Longer for UWA, shorter for bigma, etc. Beyond this though, I honestly can't tell you much more yet... need to use it more first I suspect that what you say about moving at different rates maybe true, there are quite a few ifs and buts I've been reading about googling it so I'm sure I'll report back in due course when I have more of a clue

... then it moves the sensor for you in B mode, based on the mm of the lens data, at the same speed stars move on the sensor, so the stars stay put. Like an inbuilt equatorial mount, which is the thingamygummy that follows the stars when you're looking through a telescope.

I can't say for certain as I havn't played enough with it yet, but I should think it's unlikely that in-camera HDR would work, because it has to be on bulb mode. But HDR blending on a PC after the fact should be ok, you might lose a little negative size because of star movement but beyond that I don't see any reason why not?

Sorry, I have not put any up yet but yes, even after one night I've managed an ok photo without any stacking. It's dead easy, as Francois says, switch it on, get signal ("calibrate"), put camera on B and shoot a shot on B. I managed a couple of ok shots (good enough that wife wants it as her desktop pic) although I'm after a higher standard myself so will probably go the whole hog with blending and stacking before I put something vaguely ok up. Oh and it's the wrong part of the year for a nice milky way shot and where I live is the wrong area. But to answer your question, very easy to use for a basic stars in the sky type shot.

I just bought one of these too and although I was less than overwhelmed by the manual on how to use it, I figured it out after a bit of googling around. For me it's just a tool to get non-trail milky way backgrounds to blend them into night shots and I think for this sort of simple purpose it looks ideal, and dead easy to take to location. One slight issue is that I'm about an hr south of London and shooting north is just a waste of time because of the light pollution, but hopefully I'll find some spots nearby to shoot in other directions. I actually bought it for this comet but I guess we'll see if anything is eventually visible

Damm!

And my astrotracer thing arrived today