In astronomy, a photometric system is a set of well-defined passbands (or filters), with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used. For each photometric system a set of primary standard stars is provided.
The first known standardized photometric system is the Johnson-Morgan or UBV photometric system (1953). At present, there are more than 200 photometric systems.
Photometric systems are usually characterized according to the widths of their passbands:
- broadband (passbands wider than 30 nm, of which the most widely used is Johnson-Morgan UBV system)
- intermediate band (passbands between 10 and 30 nm wide)
- narrow band (passbands less than 10 nm wide)
Read more about Photometric System: Photometric Letters, Filters Used, See Also
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