Part 2,
Here are a few other considerations to take into account.
The faintest stellar magnitude is dimmest star the telescope can see in ideal conditions. The best resolution is roughly the minimum separation of of objects (such a double stars) that the telescope can resolve in ideal conditions.
Another thing to keep in mind is that a larger mirror is harder to figure and takes more time to grind.
The average beginner mirror is either six or eight inches in diameter
