LIFU throughput, SNR calculator

The net throughput of WHT + WEAVE is expected to be 0.25 - 0.33 in low-resolution mode and 0.10 - 0.25 in high-resolution mode, depending on wavelength. The commissioning results so far are consistent with these predictions. The WEAVE signal-to-noise calculator can be used to predict SNR per A as a function of apparent magnitude, band, spectrograph mode, readout noise, airmass, seeing and sky brightness.

When using the calculator, bear in mind that the apparent magnitude to be entered is the surface brightness averaged over a 2-6-arcsec fibre. I.e. if the targets are star-like, the mags need to be converted to surface brightness, i.e. add Δ = 2.5log10(fibre-area). The fibre area = 5.3 arcsec², so Δ = 1.8 mag.

Useful tabulations of results from the calculator can be found on this page provided by Scott Trager.

Chris Benn, Lilian Domínguez, Cecilia Fariña