I have one of these lenses that I picked up used for really cheap. Forget handholding, and for the most part I don't think they'll work for your dish tracking project.
In no particular order, here are some of my observations.
You need a rock solid tripod to use this lens. Really solid. Like granite. Better yet, set it on a brick wall far from traffic. Any motion will cause your image to bounce. Even a gentle breeze. Mirror bounce will set it off too.
This is a completely manual lens, and you can't adjust the aperture. Yeah, it says f8-f16, but what that means is that as you zoom (another thing entirely) the aperture changes. It's always fixed at as wide as possible, there is no iris inside.
Speaking of manual lens, it's manual focus. With this lens that means "you will have to continuously refocus manually" while trying to shoot. Always. Think you can just throw it to infinity and hit the moon? Ha. Nope. You have to focus on the moon.
The lens is constructed such that temperature changes will affect focus. You can watch the lens go out of focus as the lens cools or warms.
The lens is soft. As others have said, you'd probably get a sharper image out of a 400L and some cropping.
To zoom the lens you have to loosen a locking collar, slide the barrel out to the marked length, and re-tighten the collar. The collar is not the highest quality, and the tighten/loosen thing is sometimes like taking the lid off a pickle jar.
So that's the good points. Ha. Just kidding.
This lens is a monster, and if you get the right one it's that nice Canon off-white. As such, it will get attention from everyone around you.
It comes with a tripod mount and you can spin the whole thing to switch from portrait to landscape (as a good tripod mount should).
I haven't noticed flare problems.
The front element is a big honking piece of glass that is kinda impressive.
You can take pictures that are passable if not good, from 4 miles away.
Some of the moon shots in this gallery (mostly the first few, I think) were taken with this lens or the lens plus the 2X converter. http://www.jongilchristphotography.com/Places/Nature/Astronomy/14675037_9bnkFK
Picture number 26 in that gallery is Touchdown Jesus at the University of Notre Dame from about 2.1 miles away.
This picture is the Golden Dome at ND from Rum Village Park about 4 miles away. It was a clear but cold day and kinda windy. This was one of the first pictures I took with it. http://sphotos-b.xx.fbcdn.net/hphotos-prn1/76915_1573142581385_3504694_n.jpg
My overall take on this lens is that it's fun to have and play with, but not something you will use very often. I'm considering selling mine as it hasn't been out of the my closet for over a year. If you have any questions, feel free to PM me or ask here.