Night Sky Shooting / Astrophotography on X-T2 : ETTR? ISO 1600?

I think you missed my point & I'm not giving Roger's advise. I recommend for consistent color - whatever you choose - set the final WB in post including Auto WB. Using fixed daylight WB in camera is safer because it gives the same color balance for all your subs for stacking or stitching. W/ auto WB in camera, small changes in scene brightness or color such as air glow can make your subs hard to match due to color variation. I've often had a thought time getting good blends in the sky when stitching. Auto WB during capture makes that more likely. And if your Astro includes Aurora, you really do want to use daylight fixed WB in the camera. Having jpgs is especially helpful for Aurora.

From my experience, how daylight WB works out for Astro depends lots on the camera. The results Roger gets out of Canon looks like what Canon using members in my club get. On my Olympus, XT10 & a rented XPro2, Daylight WB produced excellent sky color. On my XT2, it's pretty terrible especially if there is any LP. I rented the XP2 before the XT2 came out thinking they would be the same - don't think so. Daylight WB reports a different Temp & tint in LR For my XT2 than the XP2. I do get the muddy brown sky you speak of from the XT2 unlike all the other cameras I've used.

Just got a color passport to check the color profile of my XT2 because of this. Wish I had an XPro2 so I could do a compariason. The XP2 also has less black clipping than the XT2 - see Photon to Photos. If it had a flip screen, I buy one.