Other Advantages of
ugriz
•H-alpha falls in “r” and H-beta and H-gamma both fall in “g”.
•The “u” filter is broader than
Johnson U. The
two main metal lines in stellar spectra (from calcium) fall inside “u”.
–So,
photometry in ugr
allows the metal content of stars to
be determined with great precision.
–ugriz photometry allows the physical parameters of
stars to be determined without spectroscopy (from
CCD images in large surveys).
