How many stars are visible at night - depend on the night and where you are on earth, how good are your eyes, what is the elevation/how much oxygen do you have - no smoking or alcohol, and, and, and. The number of stars brighter than some value is known. Still with individuals being just that the value has to be calcuable or measureable in some way. So for the Leonids coming around Nov 17 there are areas in the sky where you can count stars, refer to a table of number of stars as a function of magnitude and determine how faint you can currently see.stars and hence meteors. Your sightings can then we scaled up to what an ideal observer would/might have seen if the radiant had been at the zenith.
how many starling did I see? I took 2 photos and counted the birds in
1/16 of the area and scaled to the toal image - too lazy to count all
and anyway I have enough trouble counting to 6 to play "Chop Sticks" -
easily challenged, as it were.
So here is an estimate of 640 starlings:
And here 800: