Jecht spheres around Spira: Locations

[Ouch!]

I want to find and watch them all and I was wondering if there is a way to tell me where some are without being spoileriffic.

Do some of the spheres become findable after certain events>?

If I remember correctly, all spheres become findable after the event in which Auron reveals their existence to you.

You'll have to do some backtracking to get them.