How does one prune a mountain ash?

Question:I have a small tree, that has 2 main branches that form the trunk. I have read that one should be removed.

Answers:
I did this today, I cut with my chain saw and carved the tree so it has 1 trunk. I like the look of Mountain Ashes when they are trimmed with just 1 trunk. I did not cut too deep, and left a tiny ridge above the trunk. I think it looks awesome, can't wait to see those beautiful orange berries like every year.