cosmo_calc.py: Use variables H0, Om0, pixelsize
cosmo_calc.py: Use variables H0, Om0, pixelsize

TODO: add argument --pixelsize with default value of 0.492 [arcsec]

liweitianux/chandra-acis-analysis,liweitianux/chandra-acis-analysis,liweitianux/chandra-acis-analysis