Hmm, well you could try the wider apertures then. I would throw some
dim light into the mix, just a little, so that you aren't so dependent
on the tree lights as a source, and can get a shorter exposure. I
haven't done a tree before, but when I do "night" photgraphy, I really
shoot more like at dusk so that you get a darkish sky, but something to
light the buildings just a little.