Hi Russ,

Welcome to the world of ACP!

Here's one way to get what you want. You could calculate the "horizon" that corresponds to 2 airmasses (it'd be about 30 degrees) and then set the "Min.elevation" in the ACP/Prefs/Telescope tab to that elevation. Then when the telescope runs into that horizon limit in the West, it'll stop (if that's the end of the script) or go on to the next object.