Photometric Letters
Each letter designates a particular section of the electromagnetic spectrum; most of these sections fall within the region spanning the near-ultraviolet (NUV), the visible and the majority of the near-infrared (NIR).
Indigo and cyan are not standard colors. Orange, yellow, and green fall under visual bands, while violet and purple are under the blue bands. The letters are not standards, but are recognized by common agreement among astronomers and astrophysicists.
| Filter Letter | Effective Wavelength Midpoint λeff For Standard Filter | Full Width Half Maximum (Bandwidth Δλ) | Variant(s) | Description |
|---|---|---|---|---|
| Ultraviolet | ||||
| U | 365 nm | 66 nm | u, u', u* | "U" stands for ultraviolet. |
| Visible | ||||
| B | 445 nm | 94 nm | b | "B" stands for blue. |
| V | 551 nm | 88 nm | v, v' | "V" stands for visual. |
| G | g, g' | "G" stands for green (visual). | ||
| R | 658 nm | 138 nm | r, r', R', Rc, Re, Rj | "R" stands for red. |
| Near-Infrared | ||||
| I | 806 nm | 149 nm | i, i', Ic, Ie, Ij | "I" stands for infrared. |
| Z | 900 nm | z, z' | ||
| Y | 1020 nm | 120 nm | y | |
| J | 1220 nm | 213 nm | J', Js | |
| H | 1630 nm | 307 nm | ||
| K | 2190 nm | 390 nm | K Continuum, K', Ks, Klong, K8, nbK | |
| L | 3450 nm | 472 nm | L', nbL' | |
| Mid-Infrared | ||||
| M | 4750 nm | 460 nm | M', nbM | |
| N | N1, N2, N3 | |||
| Q | Q' | |||
Read more about this topic: Photometric System
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