Distances to the Stars - Summary.

The last day of observation lab #1 is coming. For just this time I decided to extend the observations to Tuesday. So if you didn't make it to do observations yet, hurry up!
 

Regarding subject matter: 

How to measure distances to stars?

I. If we know what the power of the star is , we may measure its intensity. 

(use a tray of water in the sun for one second, energy from the sun warms water with several Joules in that second. Each calorie ~ 4 joule raises temp of 1 gram of water by one degree. So I may measure intensity with a thermometer! Can do similar thing with star light.)

SO I know I. What do I do with it?

I=Power/4piR^2, R the radius of a humongous sphere! (the distance to the star).
From that:
R^2=Power/4pi I
R=sqrt(Power/4pi I). 

So why do we need parallax?

Independent confirmation! Who tells us that the stars really are that far? Maybe they have the same spectral type, but NOT the same power? We have only one sun to compare with!

Also, we have no idea what the power of stars not exactly like our sun is.
 

So, need parallax. Explanation of tutorial III (click here) will give you most of what you need to know.
The rest, you may read by clicking here.