Yes, moon photography is a fascinating topic. I’m looking forward to your answer, @buddingphotographer, on the stacking. I had the same question!
As for aperture, I have heard the same thing, @SarahLeePhoto. The understandable factor here is that the wider the aperture, the more light it allows in; at night it’s dark so you need something that can capture more light. But another reason for the wide aperture is so that I can reduce my ISO. Remember the idea behind ISO, “as low as possible while as high as necessary”? The more light I let in using a wide aperture, the lower I can bring my ISO which would result in less overall grain which would be considered a higher quality picture.
A wide aperture also results in a shallow depth of field, but that doesn’t play into astrophotography much because the stars are so far away the focus can essentially be set to infinity.