Age of cluster

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+');

... ...

```