"Greg Goodknight" wrote in message
hlink.net...

6 degrees, at the equator, is 24 minutes, do the math (remember, 360
degrees in 24 hours) but that's at the equator.


No math required, read the regulation.



When Grass Valley (O17) had a night
closure a few years ago over a trees and obstruction light snafu,


SVFR is not available at O17.



I pressed the issue with the local FSDO; they came back with
30 minutes being the rule of thumb they use in the 48 states.



The US has fifty states.

It's not a "rule of thumb", it's a regulation. The regulation clearly
states that fixed-wing Special VFR operations may only be conducted between
sunrise and sunset (or in Alaska, when the sun is 6 degrees or more below
the horizon) unless the pilot and airplane are capable of IFR flight.