What telescope would I need?

I see a lot of aircraft flying when I am smoking out on my porch but they are much too far away for me to identify them reliably. Assuming the planes are 5 miles away and about 5 miles up I assume I wouldn’t need the Hubble Telescope to get a clear view of the planes.

So what kind of a telescope would I need? Would a telescope give me a clear enough view such that I could identify the aircraft?

You’d be better off with a good pair of binoculars, instead. For one thing, astronomical telescopes don’t bother to correct the image inversion that occurs naturally in such optical systems, since doing so introduces more complexity which means increased losses. Additionally, 'nocs are generally more compact and easier to handle, which is a bonus when viewing moving objects, like planes. A good pair of 8x35s should be sufficient for the purpose.

You’ve got a bit of a problem. Any telescope with enough power to view the airplane is going to have a small field of view. That means the plane will fly through your telescope view to the other side in a very short time. You will also only be able to cover a small portion of the sky at a time. The odds of a plane going through any spot you aim at is going to be low.

With lower powers and some skill at identifying plane sihlouettes, you might find out what’s flying overhead. Look for a shorttube refractor telescope with a decent image erector.

A more expensive recommendation would be a pair of zoom binoculars that magnify upward of 20-25 power. You’ll definitely notice the fine trembling in your hands, but the added power will reward you with much more detail. If a rock-solid image is your benchmark, image-stabilization glasses are more affordable than ever.

Some binoculars can be mounted on a standard tripod which will add stability. I suggest a video head with fluid damping for smooth movements rather than a 3-way head designed for still photography.