This is beautiful, though not easy in a second language.
Stallworthy is comparing the sun and the moon to fruit.
Looking at the crescent moon, he thinks about the shape of the rind of a lemon, or other fruit.The 'rind' (or more commonly 'peel' )is the part of the lemon you take off before you eat it.)
Looking at the sun, he thinks about the skin of an orange before you peel it. 'Pitted' means with tiny holes or dents in it - so he sees little dots in the orange sun.
Hope this is useful to you.