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Photometric zero points

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Imaging throughput for NIRI is tabulated in the form of photometric zero points for JHK bands. Zero points are given by

mstd = mzero - 2.5 log (N/t) - k (AM -1)

where N is the background-subtracted number of ADU within the aperture, t is the exposure time, AM is the airmass. The extinction coefficients k were taken from Leggett et al. (2006). Magnitudes were measured within an aperture that is equal to 4 times the FWHM of the images, so they are insensitive to seeing variations.

The data files and plots below contain all data since the beginning of 2009 run through an updated instrument monitoring pipeline which was introduced end of 2017 to replace the one running at that time developed in 2009 (see here for more details). The new pipeline takes now non-linearity effects into account so the zero points differ slightly from the old ones. It can now also handle M' and L' band. The data files now come in two flavors. For each filter the pipeline calculates a nightly average (as done by the old pipeline), but it also provides the full results, i.e. for each individual image all the relevant information are listed (see here for more details). More information can also be found on Gemini's NIR photometric standard stars page.

Note: January 28, 2019 - We recently have identified a potential offset in the calculation of the f/32 JHKY photometric zeropoints reported on this website. We believe the values should be closer to the f/6 values reported here. We recommend using your own calibration standards for f/32 at this time. We are working on recitifying this issue in the calibration pipeline for f/32 zeropoints.

For the data, follow the links in the table below:

Camera Band



F/32 J nightly averages Click
F/32 H nightly averages Click
F/32 K nightly averages Click
F/32 L' nightly averages Click
F/32 M' nightly averages Click
F/32 all full results Click
F/6 Y nightly averages Click
F/6 J nightly averages Click
F/6 H nightly averages Click
F/6 K nightly averages Click
F/6 all full results Click

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