Hi Ellen, as you can see from all of the differing rules you've encountered, there is some flexibility. Typically, you measure from the center of the fixture's electrical junction or, in this case, the center of the canopy of the fixture. (Btw, your electrician will thank you! ) The key is to how the light will be spread across the whole of the island. Generally speaking, using #2 will give you the best results. The lights are each "covering" 30 inches to the right and left so all areas of the island are illuminated.

Two similar projects:

Impactful Addition, Kitchen · More Info

spaced 23" 41" 23"

And,

Elevated Style, Kitchen Remodel · More Info

spaced at 27" 45" 27"

On a 10' island I'd do 3 lights, not 2.

all depends on how wide your pendants are going to be. Seems like you would have a large space at either end. 1-2' would be max for ample lighting. yours are 17" wide? I think you could do 3 with that size island. see 2nd to last pic

although, this looks more like 8'

another huge island/pendants

these look to be 10" and they've done two.

but, here is 3. I think you could do 24-30" between each one, and at least 12" from end

Thank you all for your input! It sounds like #2 (30 inches from each end) makes the most sense.

Yes, and that is 30 to the BOX.

The hanging lantern in polished chrome tends to reflect everything around it and become invisible. Having the fixture in an alternate finish will make a better statement.

Sometimes the long lantern style looks very good over long islands.

BeverlyFLADeziner - what finish would you recommend? My ceilings aren't vaulted so I originally chose these fixtures so that they (while present) don't break up my space too much. Could I still achieve this look with a different finish? I am also planning to put the long lantern above my dining room table - would you ever consider doing a long lantern over a dining room table and over an island?

If you use the long fixture over the table, then using the lanterns over the island make sense. I don't know the design of the kitchen but the bronze or black finish could be options.

Circa lighting has both lantern and linear in gilded iron and in bronze. A nice complement to stainless apps in the kitchen, either finish.

It looks like you may have solved your spacing dilemma based on previous comments in the thread. With that, if you're interested in a big open lantern look but in a different finish, we do have these options from the Savoy House Townsend family.

Satin nickel (not as polished/reflective as the finish you showed above, but very similar)

Warm brass

Classic bronze

Matte black (a new and very chic look!)

I'm personally very fond of things finished in brass or black--they just look so stylish!

Sorry but honestly those fixtures do nothing for providing actual lighting over a large island they light the ceiling not the work surface .Your island will be a work surface for sure and IMO you need task lighting over it. So look for some pendants in that size with downlights.