I was shooting smaller apertures and lower iso with the hopes of decreasing CA (which did in fact work, though it wasn't eliminated completely). The biggest surprise is, that once normalized for exposure, the images shot at f2.8 had just as many stars in them as the images shot at f1.7. I really couldn't distinguish a difference in even the faintest stars. f1.7 had less noise in the black but the stars at f2.8 were definitely more pinpoint and sharper (and like I said the CA issue was partially resolved).
This is pretty much exactly what I would have expected. Most lenses are sharper when stopped down a bit and you would expect a little more noise or at least a worst signal to noise as you are decreasing the signal and keeping the noise the same. It's always going to be a trade-off. Stopping down will also make the focus a little less hyper-critical, nailing the focus is way harder than most people would imagine.