I have a QSI583ws, which does NOT have the OAG feature, but I know people that have that version (wsg) and like it. The OAG, by the way, is not new. The new 600 series is mainly different in that it offers a selectable faster download speed. That's a big help for focus and framing as the standard download is very slow.
Derek is right about using parfocal filters. The other thing about this built-in OAG is that it is not adjustable, other than by rotating the whole camera. In that sense, it is like the SBIG dual-chip cameras, but QSI puts the OAG pick-off in front of the filters. I'm thinking about trying an OAG, but would probably go with a separate OAG unit.
If I read the ads correctly, I think that the 600 series will also have a) better cooling, and b) the larger body can have an 8-slot filter wheel, rather than a 5-slot filter wheel (no need to open camera up to change from narrow-band filters to an LRGB set)
A question: Is the pick-off prism in the QSI cameras larger than most pick-off prisms? Can one get a larger field of view for the guider than one would get in a dual-chip SBIG ccd camera?
That depends on how you define "good"! The QSI cameras have about the lowest noise out there and that is partly due to the slow read time (A-to-D conversion time), which directly limits the download speed. The problem is that the camera is low whether or not you care about the noise level. So the new model lets you choose slow for important frames and fast for things like focus, framing and exposure checks.
The other great thing about the QSI cameras is that the integrated filter wheel puts the filters so close to the chip that (with the very popular KAF-8300 version) you can use 1.25" filters in most cases, saving a lot of money over 2" filters.
Yes, I think the cooling is improved (although I'm quite happy with mine in that respect). The larger body option for 8-position filter wheel is nice, but not worth the extra money for me.
I don't know about the guider field of view, but would guess that it's quite small. Of course, you can choose different sizes of guide chip in this case (i.e., different guide cameras), while the SBIG is what it is.
For those contemplating the wsg models from QSI, just make sure you install filters that are precisely parafocal, Otherwise you will need to change focus when changing filters, which also changes the focus for the off-axis guider. And who wants t have to refocus their off-axis guider during an imagine session, right?
I don't have a QSI, but I have seen a lot of pics on the web taken with QSI cameras, and it is clear that they are excellent cameras and the off-axis guiding system works very well. The only downside to QSI is they don't have an IR preflash to control RBI (although many imagers have reported that it isn't a big problem for them) and QSI has not yet released their 700 series cameras with the larger ccd chips like sbig and FLI etc have.....