I broke out wikipedia for stellar classes and tried to work out a formula for the Zenith<->planet distance based on star mass and luminosity.
Schwarzchild geometry would suggest something like distance = C*sqrt(mass) where C is a constant. This is very wrong with an extreme case being the B0V given in Strat ops page 70. A B0V is 17.7 solar masses, which would suggest 42 AU, but it's listed as 2318.96AU, missing by a factor of 55.
Eyeing things, distance = C*sqrt(luminosity) is closer---that gets within a factor of 5. Fiddling a bit further, distance = C*Luminosity^0.62 gives a factor of 3.5 approximation.
Throwing in mass and luminosity together so distance = C*mass^a * luminosity^b and solving for a and b, you can get a factor of 3ish approximation using C*mass^-3.05*luminosity^1.43. That's not much better given the effort.
In retrospect, luminosity dependence is more consistent with charging times which varies over just a 40% range. Using the recharge times, I can get a factor of 2.4 approximation via distance = C*sqrt(luminosity)*(solcharge time/recharge time)^5.
Overall, there's no clear exact formula, but sqrt(luminosity) (~= solar power incident on the Zenith) is the closest easy approximation, with the distance somewhat longer for small stars and shorter for large stars.
