"How are your Indigos getting enough calcium to make good eggs?"
like most vertebrates, the bone is the major calcium reservoir. calcium is mobilized from this store when calcium levels in the blood start to drop, when calcium in the blood starts to rise it is deposited in the bone and excess is excreted by the kidneys. calcium blood levels are very tightly regulated, even small increases and decreases will cause problemns with neuronal function.
"Natural sunlight produces a vitamin that synthesizes the calcium thus making it available for the process of egg making."
UV is used for one step in the biosynthesis of vitamin D3. this vitamin (actually a hormone) signals the intestinal epithelium to synthesize calcium channels so that calcium can then be absorbed from the diet (calcium is an element and cannot be biologically synthesized). remember that the animals we feed to our snakes also contain vitamin D, which offers some assistance to calcium absorption.
matt