No need to keep a wet edge. For that matter it would be next to impossible with what you are using

So, Christopher, should I just start on one side and move to the other, or work in quadrants like I was thinking? Also, is there a trick to keeping track of where I have painted? I think that is the hardest thing for me when painting a ceiling, especially with the second coat!

Second question ... is painting a vaulted ceiling with a roller a dumb idea?

There you go^^, and there should be no reason to be doing 2 coats with what you are using.

What do you mean when you say you roll in "the direction the sun shines?" I' don't really understand what that means.

"What else would you paint it with? "

Well, I wouldn't (and couldn't) use anything else, but I thought maybe pros sprayed ceilings instead of rolling them ... ? Painters tape is a good idea for marking off the lines, I'll try that. And I never paint less than two coats regardless; I just can't do it. :-)

If the sun comes in the windows from north to south, paint either north to south or south to north. Just do half the ceiling at a time, no need to mark it off, also a waste of time and $ to be putting 2 coats on the ceiling( unless it NEEDS it). Just my opinion form someone who has been doing this for almost 30 years, daily. Also do not use anything less than a 1/2 in nap roller cover.

Haha Christopher, take it from someone who does NOT paint daily, while it is possible that I won't miss a spot or two on my first coat, it isn't likely. But I will take your advice into consideration and look closely before tackling a second coat. I used BM flat ceiling paint with a 1/2 nap roller on the other ceilings per the advice I received here with excellent results! They were all just flat 8 ft. ceilings though, so much easier. And thanks for clearing up the "direction" thing!

Have fun.

Well I have never had a problem seeing what I have painted and what I have not painted. If you walk away a bit from the ceiling and look at it, you should be able to see the wetness of the paint because it is shiny there and the areas that are not painted are not shiny? You just need to be far enough away so that you can see the applied paint at an angle. Some people have said that you need to roll parallel with the light source (windows) but I have not found this to matter which way you roll it.

Haha, I was looking for a way to get around the "walking away to look at it from a different angle" thing! I'm hoping the wet areas will be easier to see on the vaulted ceiling!

You just need to be far enough away so that you can see the applied paint at an angle. Some people have said that you need to roll parallel with the light source (windows) but I have not found this to matter which way you roll it. I agree