How many? Depends on:
- Where you are (Smallville is probably relatively low on light pollution, so you can get dark enough nights to see the stars pretty well, as long as the house's exterior lights are off)
- How cloudy it is (you can't really see clouds at night, but they do block the stars)
- How bright the moon is (you'll see a lot more on a moonless night than you would on a full moon)
- What time of year it is (different star patters appear on different days as the world goes through its orbit)
- How good your eyes are (not just distance but night vision)
With Clark's eyes, he can probably find quite a few more than a human. He can't see in the dark, but he's got very good night vision, which means he should be able to see some of the dimmer stars that aren't normally visible. Telescopic vision will, of course, also be of help.
There's another trick. We live on the outer edges of the Milky Way galaxy. There are relatively few stars around us, but the closer in to the center of the galaxy, the more stars you'll see. If you're in the right place at the right time, (again, time of year matters, along with position on the globe) you should be able to see towards the center. Most people will see only a white streak in the sky because the stars are packed so closely (that streak, also called The Milky Way, is the reason for the galaxy's name), and I doubt that most of those stars are named on the list. Clark's eyes just might be good enough that he could pick out individual stars (at least on the edges). That would dramatically increase his count, assuming he managed to keep an accurate count.
So, how many? You got me.
Sorry. I think you'd be safe picking whatever number suits you. If most humans can see 6-10 thousand, depending on various conditions, then Clark should be able to see 15-30 thousand, maybe more. He'd probably be able to see even more if he flew upwards, since the atmosphere makes stars harder to see (which is why observatories are placed on high mountains and why the Hubble was placed in orbit).
How long would counting take? At normal speed, hours. Maybe even more than one night. 30,000 seconds is 8 hours and 20 minutes. When stars are closer together, he could probably count a few per second, but if we're assuming he's going slowly and carefully, scanning as closely as he can, then there are going to be times when it goes a lot more slowly than that.
This, of course, means that he has to be able to stand in once place for that long, accurately remember his count even as it gets into the thousands, and remember whether or not he's counted any given star yet. Luckily, he has a super memory, but it's up to you to decide if even Clark's memory is up to that task.
At Super speed? Up to you. There's no defined limit to how fast he can move his eyes. We know he can move his body at least a hundred times faster than normal (see
here for a quick look at just how fast a speeding bullet can be... 1000 meters/second seems to be a good number for a "speeding" bullet. In contrast, the world record for the 1000 meter dash is just under 132 seconds), but we don't know about just his eyes. Assuming he can move his eyes 100 times faster than normal, and assuming the figure of 30,000 seconds for counting, then he should be done in 5 minutes. That's based on a *lot* of assumptions, though, so feel free to make it shorter or longer as you see fit. All we really know about his eye speed is that he can read a whole stack of research notes in a few seconds.
So, there are some rough numbers to get you started, but ultimately, there's enough flexibility for you to say whatever you want.
Paul
