Estimating relative distances for star clusters

[randa177]

If star clusters were all about the same physics size, how could one estimate their relative distances?

 

[mgb_phys]

Either by measuring their angular size or apparent brightness.

 

[randa177]

would the distances determined geometrically give the same result as those determined photometrically (using stellar brightness relation)?

 

[mgb_phys]

If they were really the same physical diameter then the advantage of measuring their angular diamter is that it isn't affected by anything else ( assuming it is large enough to be detected above atmospheric seeing)
The problem with measuring brightness is that you have to make assumptions and correct for the absorption and re-emmision from the space in between (Interstellar reddening).