i cant get happy with my top dome tring to keep it all a single mesh, though like my daedalus im gonna do most of the details with textures, as i suck at boolean
If you start the model as a sphere, or more precisely a hemisphere, and then extrude the saucer from there your dome will be perfect and the model will be one piece.
Or
Make a hemisphere that's the same number of divisions as the saucer and place it where you want it. Delete the inner polies from the saucer where the dome intersects it. Then manually connect everything.
Booleans are hard to get. I used to really struggle with them. I got some simple, but good advice from Adonis. He said, "Don't be afraid to get in there and do some hand stitching". Often you have to to clean them up. That shape is simple enough though that you should be able to avoid a boolean.