# What does the filter name I+z' mean

On the TRAPPIST telescope, the filter wheels are described to have a filter with the following description:

NIR Luminance I+z' (>700nm)

After a bit of googling, I wasn't able to find what the specifics of this filter are (its FWHM and mean wavelength).

How would I go about finding these qualities of this filter?

• the (Bessel) I filter which has a central wavelength of $\lambda \simeq 800\,\mathrm{nm}$ and a width of $\Delta\lambda\simeq 150\,\mathrm{nm}$, and
• the (Sloan) z' filter, which has $\lambda,\Delta\lambda \simeq 970,255\,\mathrm{nm}$.