Spinning, you can see where a dark grain makes it look like there is a thick piece of wood between two cutting areas. Stop the lathe, look, and do not cut too thin or for that matter through the side of the vase.
Advanced Woodturning Project
Black Cherry Vase - Page 5
being careful to know what is thick wood and what is grain
Continue the cuts...
and balance the light through the walls. Here you can see what a difference the grain can make through the walls.
Now I have to make some decisions about the shape of the vase and where it is going to begin and end. The screws are in the base but they can be treated as nuisances and the screw holes turned away with some planning and fore thought.
I clean down past the bottom and leave room for design and consideration of the base.
A slight cove assigns a height to the base and marks the depth of the interior so as not to cut through later when the scrap around the screw holes is removed.