Age of cluster

Contents

Cluster HR Diagram

Now you should have both the isochrones and data from cluster NGC 188. To remind you what are the variables, use

whos
  Name           Size             Bytes  Class     Attributes

  isoc           1x1             144232  struct              
  myCluster      1x1             469052  struct              

Let's make a HR diagram for NGC 188 by plotting V vs. B-V (don't forget to reverse the y-coordinate):

figure(3); clf;
plot(...);
set(gca, ...);
title('NGC 188');
xlabel('B-V'); ylabel('V');

Isochrone Matching

Look carefully at the turning point of the main sequence, compare with your isochrones, and find out which isochrone has the same B-V value of the turning point.

figure(4); clf; hold on;
plot(..., 'm+');
plot(..., 'r+');
plot(..., 'y+');

... ...

Now, consider the difference in V value between cluster NGC 188 and the isochrone you chose. Move the isochrone up and down to find the best matching:

figure(5); clf; hold on;
plot(..., 'bo');
plot(isoc. ... .B-isoc. ... .V, isoc. ... .V+10, 'm+');
plot(..., isoc. ... .V+11, 'r+');
plot(..., isoc. ... .V+12, 'y+');

... ...