Pruning a Mountain Ash in my backyard

I have an old Mountain Ash in my backyard of the house I bought 2 years ago. I don't know HOW old it is though.

Anyways, I've got some dead branches. Some of the dead branches are only dead on the last 3 or 4 feet of the branch. Can I just cut the dead part of the branch off or do you cut the whole branch from where it grows out of the main branch?

I also cut off all the tiny lit new shoot branches that were coming out of the lower 6 feet or so of the main trunk. These were little thin green branches maybe 1 or 2 feet in length.

So also if I've got a branch that's growing out in a place I don't want it, for example one branch is growing out right over an above ground pool. Can I just cut it off? Do you cut it off anywhere or cut the whole branch off?

Also. Should I prune it only in the winter or is it ok to do now or later in the fall?

Thanks

 

Well, generally, you prefer to prune a tree that drops its leaves in winter when it's dormant, but as a practical matter, nobody worries about pruning unless it's some sort of fruit tree or flowering tree.

When you prune, you always want to cut at some form of " Y " junction, removing one part of the Y and leaving the other. The branch will heal quicker than if you cut a blunt stub.
Cutting to stubs generally results in one of two undesirable things happening.
Either the stub dying back to the joint which can start to rot the limb;
or the stub lives and you get a "pollard" effect with lots of little sprouts come up, (ie. the end of the branch looks like a some sort of sea anemone) and those whips grow straight up, and also break off very easily.