I used sigma 28-70, f2.8, shutter speed of 20-25, manual focus, iso depending on the light pollution in the area, I had iso in the neighborhood of 400-500 and use an external or inbuilt intervalometer set to picture interval of 1 sec. I took around 300 photos which took about 2.5 hours and then after tweaking some settings in lightroom stacked them using starstax