Do you need to focus stack at night (with an aperture of F1.8)?
You certainly can focus stack in this situation and produce excellent results. And this may be your best option if you’ve set up your composition after it’s already dark. However, what I find much easier is to set up my composition while it’s still relatively light out, like during twilight. Then I can take a single exposure at f/8 or f/11 or f/16, ISO100, and 30 sec to a few minutes. Then once night has fallen and the stars come out I take another shot at ISO3200, f/2.8, 30 seconds or so to get the stars. Then I can blend those two shots in Photoshop later; much simpler than blending 10 focus stacked images at f/2.8. Not to mention it produces better image quality because of being at a low ISO.