View source for Central wavelengths and zero points

Here is a large collection of central wavelengths and zero points, useful for converting between flux densities and magnitudes, which then enables adding points into an SED, or making a color-mag diagram (depending on whether you are starting from mags or flux densities).

 band     wavelength (um)    zero point (Jy)
  J            1.25           1594
  H            1.65           1024
  Ks           2.17            666.7  Kshort not Johnson K!

  I1           3.6             280.9
  I2           4.5             179.7
  I3           5.8             115.0
  I4           8.0              64.13
  M1           24                7.14
  M2           70                0.775
  M3          160                0.159

  W1           3.4             309.54
  W2           4.6             171.79
  W3          12                31.676
  W4          22                 8.3635

  U           0.36            1755
  B           0.44            4000.87
  V           0.55            3597.28
  Rc          0.71            3080     !! Cousins R (not the same as Johnson R)!
  Ic          0.79            2432.84  !! Cousins I (not the same as Johnson I)!

  sloan u    2910*1d-4        see below    !! 2910 A, and there are 10^-4 um per A. (etc for rest)
  sloan g    4810*1d-4
  sloan r    6230*1d-4
  sloan i    7640*1d-4
  sloan z    9060*1d-4

  iphas rprime  0.624         3173.3
  iphas ha      0.656         2974.4
  iphas iprime  0.774         2515.7 

  akari band 1   9                   !! AKARI reports things already in fluxes. Generally, don't trust any other akari bands.
  akari band 2  18


BE CAREFUL to keep track of whether you are working with Vega-based magnitudes or AB mags. Vega magnitudes define things with respect to a Vega spectrum (see [[Units]] page), but some folks (largely extragalactic folks) define things with respect to a flat spectrum source instead, and those are AB mags. Most Sloan folks (even those folks working with stars) work in AB mags instead. For AB mags, you always use a flat reference spectrum, so the zero point is 3631 Jy for all bands.

[[More on filters and bandpasses]]

For advanced folks (and, frankly, my own future reference): If you have measurements from one of the USNO plate scans of the POSS plates... Monet et al. 2003, AJ, 125, 984 reports these transformations from SDSS EDR photometry [Section 8. eqn 2b-2e].

 "B" magnitudes:
 O = g* + 0.08 + 0.452(g* -r*), sigma = 0.34
 J = g* + 0.06 + 0.079(g* - r*), sigma = 0.33
 "R" magnitudes:
 E = r* - 0.20 - 0.086(g* - r*), sigma = 0.30
 F = r* - 0.09 - 0.109(g* - r*), sigma = 0.26
 "I" magnitudes:
 N = i* - 0.44 -0.164(r* -i*), sigma =0.31