•Three standard photometric bands: U (ultraviolet), B (blue), & Y (yellow-green,
now “V”).
These were the basis of modern broad-band UBV filters.
–The UBV as
defined above was refined by Johnson & Harris (1954,
Ap.J., 120, 196) and by Johnson (1955, Ann.
Astrophysics, 18, 292), becoming the standard system for all
visible photoelectric photometry and, by extension, all
spectrophotometry.
What was defined...