This lab will give you a little bit of a feeling for how many stars are visible in the night sky. It's very easy (especially if you're living in a bright city like Los Angeles) to think that there's very few stars up there - this lab will help you estimate how many visible stars are up there, based on where you live!

For this lab, you'll need to print out the How Many Stars Can You See Download How Many Stars Can You Seeworksheet - this is a pretty straightforward exercise, but there is a little bit of math that's involved - so be careful about that. Make sure that the answer that you calculate makes sense!

How Many Stars Can You See? (Unaided Eye Exercise #4) Name: Date: Materials: Hollow Tube, Ruler, Clear dark sky. Purpose: The number of stars that can be seen by an unaided eye depends on the light pollution, sky condition (clouds, haze), and visibility of sky. On a clear dark night, with a *360 view' from horizon to horizon, there are roughly 3000 stars that can be seen with the unaided eye. Here's a way to estimate how many stars are visible to the unaided eye from your location. Procedures: Part 1: Start by simply spending a few moments observing the night sky, making a mental note of how clear the sky is, and how much light pollution there is at your location. Then without doing any systematic counting or calculation, simply make an estimate of how many stars you can see in the entire sky (assuming you could count them all). Write the number here. Estimate of number of visible stars: Part 2: Now, we'll perform the estimate another way. Take a hollow tube (a cardboard paper towel tube cut in half works well), and look through the tube at the sky. Point the tube in some random direction at the sky. Count the number of stars visible through the tube for this direction, and record the number below. Be sure to give your eye enough time fo adjust to the faint light of some of the stars appearing through the tube, before counting the stars and recording the number. Then point the tube at another random location on the sky and repeat the count. Do this a total of 5 or more times, recording the number of stars counted each time. Count 1 Count 2 Count 3 Count 4 Count 5 Total Count Calculations: Here's the mathematics of how to estimate the total number of visible stars. 1. Start by calculating the average number of stars seen through the tube for each position. (Add up the stars counted for each sighting, and then divide by the total number of times the stars were counted.) Average star count = Total Count/ 5 = 2. Measure the length L, and the diameter D of the tube used to look through. Measurements can be made in inches or centimeters (or any other units), but the two measurements must be in the same units. L= D= 3. Now use the following formula to calculate the total number of stars visible from horizon to horizon from your location. Total number of visible stars = (Average star count) x (8 L2/ D2) Total number of visible stars = Conclusion: Write a few sentences below summarizing this exercise. Were you surprised by the number of stars you can see in the entire sky? Which estimate do you think is more accurate, the one made simply by looking at the sky, or the one made by counting stars in 5 different regions? Make mention of the clear the sky was, and if the sky condition changed as the night went on. Also mention any difficulties you encountered performing the exercise in general