But things
start to get complicated
•After 50
years, UBVRI is showing its age.
–It was designed for photoelectric photometers, which ceased to be used some 20 years ago.
–U
has fallen into disuse.
–I comes in almost as many varieties as ice cream.
–The
UBVRI system was ideal for observing galaxies but, is
far from ideal for photometry of stars.
•The
bands are too wide for separating the main spectral lines.
–Makes
measuring the physical properties of stars extremely difficult.
•Many
different alternative systems were thus defined (Strömgren, narrow
band, Gunn, etc). Very confusing. Difficult to compare data.
–And…
H2OV