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| Joint Astronomy Centre |
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Extinction MeasurementsTypical extinction values measured at UKIRT are given in the table below. Extinction can vary from night to night and if the difference in airmass between target and calibrator is significant then the value for that night should be determined. Historical information on extinction as a function of wavelength is also available.
Zeropoint Measurements for 5" Aperture at Airmass=1.0
The zeropoint listed below is for 1.0 airmass and is defined as
(true magnitude) = (instrumental magnitude) + zeropoint
A larger zeropoint implies a higher throughput. Small changes in
zeropoint can be expected due to sky, telescope and instrumentation
throughput variations. The zeropoint will be smaller than the values
listed below if the seeing is very poor, unless the software aperture
is increased. Observers should always
determine their own zeropoint (and extinction if necessary) for the night.
WFCAM Zeropoints (ZY not yet well determined)
UIST Zeropoints
UFTI Zeropoints
IRCAM/TUFTI Zeropoints
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