Photometric system

In astronomy, a photometric system is a set of well-defined passbands (or optical 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.

A commonly adopted 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)

Photometric letters

Each letter designates a section of light of the electromagnetic spectrum; these cover well the consecutive major groups, near-ultraviolet (NUV), visible light (centered on the V band), near-infrared (NIR) and part of mid-infrared (MIR). The letters are not standards, but are recognized by common agreement among astronomers and astrophysicists.

The use of U,B,V,R,I bands dates from the 1950s, being single-letter abbreviations.

With the advent of infrared detectors in the next decade, the J to N bands were labelled following on from near-infrared's closest-to-red band, I.

Later the H band was inserted, then Z in the 1990s and finally Y, without changing earlier definitions. Hence, H is out of alphabetical order from its neighbours, while Z,Y are reversed from the alphabetical – higher-wavelength – sub-series which dominates current photometric bands.

Filter Letter	Effective Wavelength Midpoint λeff for Standard Filter	Full width at half maximum (archetypal 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.
G	464 nm	128 nm	g, g'	"G" stands for green.
V	551 nm	88 nm	v, v'	"V" stands for 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	152 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	10500 nm	2500 nm
Q	21000 nm	5800 nm	Q'

Note: colors are only approximate and based on wavelength to sRGB representation (when possible).

Combinations of these letters are frequently used; for example the combination JHK has been used more or less as a synonym of "near-infrared", and appears in the title of many papers.

Filters used

The filters currently being used by other telescopes or organizations.

Units of measurements:

Name	Filters	Link
2.2 m telescope at La Silla, ESO	J = 1.24 μm	H = 1.63 μm	K = 2.19 μm	L' = 3.78 μm	M = 4.66 μm	N1 = 8.36 μm	N2 = 9.67 μm	N3 = 12.89 μm		2.2 m telescope at La Silla, ESO
2MASS/PAIRITEL	J = 1.25 μm	H = 1.65 μm	Ks = 2.15 μm		Two Micron All-Sky Survey, Peters Automated InfraRed Imaging TELescope
CFHTLS (Megacam)	u* = 374 nm	g' = 487 nm	r' = 625 nm	i' = 770 nm	z' = 890 nm		Canada-France-Hawaii Telescope
Chandra X-ray Observatory	LETG = 0.08-0.2 keV	HETG = 0.4-10 keV		Chandra X-ray Observatory
CTIO	J = 1.20 μm	H = 1.60 μm	K = 2.20 μm	L = 3.50 μm		Cerro Tololo Inter-American Observatory, a division of NOAO
Cousins RI photometry	Rc = 647 nm	Ic = 786.5 nm		Cousins RI photometry, 1976
the Dark Energy Camera	g = 472.0 nm	r = 641.5 nm	i = 783.5 nm	z = 926.0 nm	Y = 1009.5 nm		Central wavelengths for bands in the Dark Energy Survey
DENIS	I = 0.79 μm	J = 1.24 μm	K = 2.16 μm		Deep Near Infrared Survey
Eggen RI photometry	Re = 635 nm	Ie = 790 nm		Eggen RI photometry, 1965
FIS	N60 = 65.00 μm	WIDE-S = 90.00 μm	WIDE-L = 145.00 μm	N160 = 160.00 μm		Far-Infrared Surveyor on board, AKARI space telescope
Gaia	G = 673 nm	GBP = 532 nm	GRP = 797 nm	GRVS = 860 nm		Gaia (spacecraft)
GALEX	NUV = 175–280 nm	FUV = 135–175 nm		GALaxy Evolution Explorer
GOODS (Hubble ACS)	B = 435 nm	V = 606 nm	i = 775 nm	z = 850 nm		Advanced Camera for Surveys on the Hubble Space Telescope
HAWC+	Band 1 = 53 μm	Band 2 = 89 μm	Band 3 = 154 μm	Band 4 = 214 μm		High-resolution Airborne Wideband Camera+ for SOFIA
HDF	300 nm	450 nm	606 nm	814 nm		Hubble Deep Field from the Hubble Space Telescope
IRTF NSFCAM	J = 1.26 μm	H = 1.62 μm	K' = 2.12 μm	Ks = 2.15 μm	K = 2.21 μm	L = 3.50 μm	L' = 3.78 μm	M' = 4.78 μm	M = 4.85 μm	NASA Infrared Telescope Facility NSFCAM
ISAAC UTI/VLT	Js = 1.2 μm	H = 1.6 μm	Ks = 2.2 μm	L = 3.78 μm	Brα = 4.07 μm		Infrared Spectrometer And Array Camera at Very Large Telescope
Johnson system (UBV)	U = 364 nm	B = 442 nm	V = 540 nm		UBV photometric system
Vera C. Rubin Observatory (LSST)	u = 320.5–393.5 nm	g = 401.5–551.9 nm	r = 552.0–691.0 nm	i = 691.0–818.0 nm	z = 818.0–923.5 nm	y = 923.8–1084.5 nm		Vera C. Rubin Observatory
OMC	Johnson V-filter = 500-580 nm		Optical Monitor Camera on INTEGRAL
Pan-STARRS	g = 481 nm	r = 617 nm	i = 752 nm	z = 866 nm	y = 962 nm		Panoramic Survey Telescope And Rapid Response System
ProNaOS/SPM	Band 1 = 180-240 μm	Band 2 = 240-340 μm	Band 3 = 340-540 μm	Band 4 = 540-1200 μm		PROgramme NAtional d'Observations Submillerètrique/Systéme Photométrique Multibande, balloon-borne experiment
Sloan, SDSS	u' = 354 nm	g' = 475 nm	r' = 622 nm	i' = 763 nm	z' = 905 nm		Sloan Digital Sky Survey
SPIRIT III	Band B1 = 4.29 μm	Band B2 = 4.35 μm	Band A = 8.28 μm	Band C = 12.13 μm	Band D = 14.65 μm	Band E = 21.34 μm		Infrared camera on Midcourse Space Experiment
Spitzer IRAC	ch1 = 3.6 μm	ch2 = 4.5 μm	ch3 = 5.8 μm	ch4 = 8.0 μm		Infrared Array Camera on Spitzer Space Telescope
Spitzer MIPS	24 μm	70 μm	160 μm		Multiband Imaging Photometer for Spitzer on Spitzer
Stromvil filters	U = 345 nm	P = 374 nm	S = 405 nm	Y = 466 nm	Z = 516 nm	V = 544 nm	S = 656 nm		Stromvil photometry
Strömgren filters	u = 350 nm	v = 411 nm	b = 467 nm	y = 547 nm	β narrow = 485.8 nm	β wide = 485 nm		Strömgren photometric system
UKIDSS (WFCAM)	Z = 882 nm	Y = 1031 nm	J = 1248 nm	H = 1631 nm	K = 2201 nm		UKIRT Infrared Deep Sky Survey
Vilnius photometric system	U = 345 nm	P = 374 nm	S = 405 nm	Y = 466 nm	Z = 516 nm	V = 544 nm	S = 656 nm		Vilnius photometric system
VISTA IRC	Z = 0.88 μm	Y = 1.02 μm	J = 1.25 μm	H = 1.65 μm	Ks = 2.20 μm	NB1.18 = 1.18 μm		Visible & Infrared Survey Telescope for Astronomy
WISE	W1 = 3.4 μm	W2 = 4.6 μm	W3 = 12 μm	W4 = 22 μm		Wide-field Infrared Survey Explorer
XMM-Newton OM	UVW2 = 212 nm	UVM2 = 231 nm	UVW1 = 291 nm	U = 344 nm	B = 450 nm	V = 543 nm		XMM-Newton Optical/UV Monitor
XEST Survey	UVW2 = 212 nm	UVM2 = 231 nm	UVW1 = 291 nm	U = 344 nm	B = 450 nm	V = 543 nm	J = 1.25 μm	H = 1.65 μm	Ks = 2.15 μm	Survey includes the point source of 2MASS with XMM-Newton OM

Note: colors are only approximate and based on wavelength to sRGB representation (when possible).

References and footnotes

External links

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
Michael S. Bessell (2005), STANDARD PHOTOMETRIC SYSTEMS, Annual Review of Astronomy and Astrophysics vol. 43, pp. 293–336
, Apai, D.; Linz, H.; Henning, Th.; Stecklum, B., 2005

Photometric system

Photometric letters

Filters used

See also

References and footnotes

External links