Photometric system

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In astronomy, a Photometric system is a set of well-defined passbands (of 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 (the most widely used is Johnson-Morgan UBV system)),
  • intermediate band (passbands widths between 10 and 30 nm),
  • narrow band (passbands widths less than 10 nm).

Photometric Letters

The letters designate a region of a wavelength of light. Majority of the letters span from near-ultraviolet (NUV) to visible and majority of the near-infrared (NIR).

Note, indigo and cyan are not standard colors[1]. Orange and yellow fall under visual bands, while violet and purple are under the blue bands.

Filter Letter Wavelength range Varient(s) Description
U u, u', u* "U" stands for ultraviolet.
B b "B" stands for blue.
V v, v' "V" stands for visual.
G g, g' "G" stands for green.
R r, r', R', Rc, Re, Rj "R" stands for red.
I i, i', Ic, Ie, Ij "I" stands for infrared.
Z z, z'
Y y
J J', Js
K K Continuum, K', Ks, Klong, K8, nbK
L L', nbL'
M M', nbM
Q Q'

Used Filters

The filters currently being used by other telescopes or organizations[2].

Units of measurements:

Name Filters Link
2MASS J = 1.25μm H = 1.65μm Ks = 2.15μm Two Micron All-Sky Survey
CFHTLS (Megacam) u* = 374nm g' = 487nm r' = 625nm i' = 770nm z' = 890nm Canada-France-Hawaii Telescope
Chandra X-ray Observatory LETG = 0.08-0.2keV HETG = 0.4-10keV Chandra X-ray Observatory
CTIO J = 1.20μm H = 1.60μm K = 2.20μm L = 3.50μm Cerro Tololo Inter-American Observatory, a division of NOAO
Cousin RI photometry Rc = 647nm Ic = 786.5nm Cousin RI photometry, 1976[3]
DENIS I = 0.79μm J = 1.24μm K = 2.16μm Deep Near Infrared Survey
Eggen RI photometry Re = 635nm Ie = 790nm Eggen RI photometry, 1965[4]
FIS N60 = 65.00μm WIDES-S = 75.00μm WIDE-L = 145.00μm N160 = 160.00μm Far-Infrared Surveyor on board, AKARI space telescope
GALEX NUV = 1800-2750Å FUV = 1400-1700Å GALaxy Evolution Explorer
GOODS (Hubble ACS) B = 435nm V = 606nm i = 775nm z = 850nm Advanced Camera for Surveys on the Hubble Space Telescope
HAWC Band 1 = 53µm Band 2 = 88µm Band 3 = 155µm Band 4 = 215µm High-resolution Airborne Wideband Camera for SOFIA[5]
HDF 450nm 606nm 814nm Hubble Deep Field from the Hubble Space Telescope
IRTF NSFCAM J = 1.26µm H = 1.62µm K' = 2.12µm Ks = 2.15µm K = 2.21µm L = 3.50µm L' = 3.78µm M' = 4.78µm M = 4.85µm NASA Infrared Telescope Facility NSFCAM[6]
ISAAC UTI/VLT Js = 1.2µm H = 1.6µm Ks = 2.2µm L = 3.78µm Brα = 4.07µm Infrared Spectrometer And Array Camera at Very Large Telescope
Johnson system (UBV) U = 364 nm B = 442 nm V = 540 nm UBV photometric system
OMC Johnson V-filter = 500-580nm Optical Monitor Camera[7] on INTEGRAL
Pan-STARRS uses the Sloan's u,g,r,i,z,y Panoramic Survey Telescope And Rapid Response System
ProNaOS/SPM Band 1 = 180-240µm Band 2 = 240-340µm Band 3 = 340-540µm Band 4 = 540-1200µm PROgramme NAtional d'Observations Submillerètrique/Systéme Photométrique Multibande, balloon-borne experiment[8]
Sloan u' = 354nm g' = 475nm r' = 622nm i' = 763nm z' = 905nm y' = 1005nm Sloan Digital Sky Survey
SPIRIT III Band B1 = 4.29μm Band B2 = 4.35μm Band A = 8.28μm Band C = 12.13μm Band D = 14.65μm Band E = 21.34μm Infrared camera on Midcourse Space Experiment[9]
Spitzer IRAC 3.6μm 4.5μm 5.8μm 8.0μm Infrared Array Camera on Spitzer Space Telescope
Spitzer MIPS 24μm 70μm 160μm Multiband Imaging Photometer for Spitzer on Spitzer
Stromvil filters U = 345 P = 374 S = 405 Y = 466 Z = 516 V = 544 S = 656 Stromvil photometry
Strömgren filters u = 350nm v = 411nm b = 467nm y = 547nm ß narrow = 485.8nm ß wide = 485nm Strömgren photometric system
UKIDSS (WFCAM) Z = 882nm Y = 1031nm J = 1248nm H = 1631nm K = 2201nm UKIRT Infrared Deep Sky Survey
Vilnius photometric system U = 345nm P = 374nm X = 405nm Y = 466nm Z = 516nm V = 544nm S = 656nm Vilnius photometric system
VISTA IRC Z = 0.88μm Y = 1.02μm J = 1.25μm H = 1.65μm Ks = 2.20μm NB1.18 = 1.18μm Visible & Infrared Survey Telescope for Astronomy
XMM-Newton OM UVW2 = 212nm UVM2 = 231nm UVW1 = 291nm U = 344nm B = 450nm V = 543nm XMM-Newton Optical/UV Monitoring[10]
XEST Survey UVW2 = 212nm UVM2 = 231nm UVW1 = 291nm U = 344nm B = 450nm V = 543nm J = 1.25μm H = 1.65μm Ks = 2.15μm Survey includes the point source of 2MASS with XMM-Newton OM[11]


  1. Johnson, H. L.; Morgan, W. W. (1953), Fundamental stellar photometry for standards of spectral type on the revised system of the Yerkes spectral atlas, The Astrophysical Journal, vol. 117, pp. 313-352 [2]
  2. The Asiago Database on Photometric Systems
  3. Michael S. Bessell (2005), STANDARD PHOTOMETRIC SYSTEMS, Annual Reviews of Astronomy and Astrophysics vol. 43, pp. 293–336
  4. Infrared portrait of the nearby massive star-forming region IRAS 09002-4732, Apai, D.; Linz, H.; Henning, Th.; Stecklum, B., 2005

See also


ca:Sistema fotomètric de:Fotometrisches System lb:Fotometrescht System