A controlling edge loop is used to reduce the influence of the subdivision modifier. Carrying on from my last post add a subdivision modifier and look at the effect it has on the shape of your dome. Go back into edit mode, edges, and select the edges highlighted and subdivide. Deselect everything and select the edge loop highlighted. Double tap the "G" key to slide the edge loop rightwards towards the edge of the dome. Now you can see the effect the edge loop you just added has on the shape of your dome. You will need to add another edge loop to the bottom edges and slide the new edge loop towards the base of the dome to tighten that area up as well.

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