Errors in the zero-points are generally less than 1-2% except where ":" denotes 5% or more uncertainties, usually due to a limited amount of photometric conditions. For users who have accessed the previous version of this page click here to compare with the original table which used individual WFS run colour terms.
| Passband | Zero-Point | Colour terms | Date | Zero-Point | Colour terms |
|---|---|---|---|---|---|
| RGO U | 22.36 | -0.055 U-B | Oct 98 | - | +0.005 u'-g' |
| - | 22.28 | (+/-0.021) | Dec 98 | - | (+/-0.016) |
| - | 22.30 | - | Feb 99 | - | - |
| - | 22.30 | - | Jun 99 | - | - |
| - | 22.43: | - | Jul 99 | - | - |
| - | 22.36 | - | Aug 99 | - | - |
| KPNO B | 24.68 | -0.129 B-V | Oct 98 | - | +0.191 g'-r' |
| - | 24.63 | (+/-0.016) | Dec 98 | - | (+/-0.016) |
| - | 24.56 | - | Feb 99 | - | - |
| - | 24.52 | - | Mar 99 | - | - |
| - | 24.53 | - | Apr 99 | - | - |
| - | 24.44 | - | Jun 99 | - | - |
| Harris B | 24.12: | - | Nov 98 | - | - |
| - | 24.25 | - | May 99 | - | - |
| Harris V | 24.49 | -0.009 V-R | Oct 98 | - | -0.566 g'-r' |
| - | 24.33 | (+/-0.018) | Nov 98 | - | (+/-0.005) |
| - | 24.43 | - | Dec 98 | - | - |
| - | 24.38 | - | Feb 99 | - | - |
| - | 24.34 | - | May 99 | - | - |
| Harris R | 24.45 | +0.010 V-R | Oct 98 | - | -0.214 r'-i' |
| - | 24.17: | (+/-0.010) | Dec 98 | - | (+/-0.015) |
| - | 24.36 | - | Feb 99 | - | - |
| RGO I | 23.74 | -0.062 R-I | Oct 98 | - | -0.377 i'-z' |
| - | 23.58 | (+/-0.016) | Nov 98 | - | (+/-0.020) |
| - | 23.64: | - | Dec 98 | - | - |
| - | 23.63 | - | May 99 | - | - |
| RGO z' | 22.24 | -0.381 R-I | Oct 98 | - | +0.053 i'-z' |
| - | 22.11: | (+/-0.039) | Dec 98 | - | (+/-0.064) |
| - | 22.21 | - | Feb 99 | - | - |
| - | 22.25 | - | Apr 99 | - | - |
| - | 22.19 | - | Jun 99 | - | - |
| - | 22.13 | - | Jul 99 | - | - |
| - | 22.05: | - | Aug 99 | - | - |
| SDSS g' | 24.88 | -0.521 B-V | Jun 99 | - | -0.139 g'-r' |
| - | 24.83 | (+/-0.004) | Jul 99 | - | (+/-0.005) |
| - | 24.80 | - | Aug 99 | - | - |
| SDSS r' | 24.33 | +0.245 V-R | Mar 99 | - | -0.005 r'-i' |
| - | 24.34 | (+/-0.016) | Apr 99 | - | (+/-0.012) |
| - | 24.23: | - | Jun 99 | - | - |
| - | 24.37 | - | Jul 99 | - | - |
| - | 24.35 | - | Aug 99 | - | - |
| SDSS i' | 23.73 | +0.211 R-I | Feb 99 | - | +0.020 i'-z' |
| - | 23.57: | (+/-0.006) | Jun 99 | - | (+/-0.025) |
| - | 23.73 | - | Jul 99 | - | - |
| - | 23.68 | - | Aug 99 | - | - |
Notes to table:
An example use of the zero points and colour terms for each passband is
given below:
B'_ccd = 24.52 - 2.5 log10(counts/s) = B - 0.129 B-V
where B'_ccd is the natural CCD + filter system and B, B-V are on
Landolt's 1992 system.
Average extinction coefficients for La Palma of:
U = 0.49, B = 0.25, V = 0.15, R = 0.11, I = 0.07, Z = 0.08,
g' = 0.22, r' = 0.12, i' = 0.08,
have been assumed for the photometric nights used to derive the zero-points
and colour terms. For details of nightly individual extinction measurements
and more information regarding the La Palma extinction curve see the
Carlsberg Meridian Telescope extinction measurements.
The Z-band Landolt zero-point is in the natural WFC filter + CCD passband and has been approximately normalised to the Vega system using an extrapolated colour correction for the Landolt photometry.
The effective gain (e-/ADU) of the system is 3.12 so to convert the zero-points to photons/s add 1.24 magnitudes.
An attempt was made to use only photometric nights in deriving the zero-points but this was not possible for some runs eg. Dec 98 R-band, usually denoted by ":" after the zero-point.