The seeing at the INT is often slightly higher than this, which tends to force observers to widen the slit, and degrade their resolution. The other advantage of the 500mm Camera is that it also provides twice the resolution in the spatial direction. Although both cameras are permanently mounted on IDS, only one CCD is currently available as an option for either. IDS is offered with a choice of Tek5 or EEV10 detectors. The 500mm camera also provides higher magnification than the 235mm in the spatial direction as well as in dispersion.
Table gives the pixel scale in the spatial direction for both CCD options.
The figure below shows the results, which were consistent for each observed target. The Y-axis is the apparent AB magnitude of star observed at zenith which gives one detected photon per second per Angstrom. The collimator used was Ag-Red. In order to calculate the number of detected photons per pixel you will have to take into account the following factors. You will need to scale to the efficiency of your chosen grating at a particular wavelength.