Well, since you guys are so utterly adamant, I'll give it another try in more controlled conditions. And with a bigger stick.

I have come across other references that line up with M_a_x's thoughts (and with my initial, admittedly crude experiments). These don't invalidate the technique in any way, they simply note variations that creep in based on time of day, lattitude, and season. This, I assume, is celestial mechanics doing what it has always done.

If it works best around noon, I'll start with that. And then I'll try to get a sense of early/late results, and what kind of correction factor I should keep in mind. I don't mind that at all, provided I know what to adjust for. It's in the same vein as compass declination, which for the record I have been adjusting for long before I started posting on ETS.