1. General information on the device
2. Spectral resolutions and wavelength coverage
3. Spatial scale on IDS, and degradation of spatial profile at the CCD edges
4. Fringing and Cosmetic defects
5. Charge spreading variations and effects on spectral resolutions
6. Flux standard data and empirical through-puts
7. Quality control history of RED+2

The table linked here gives the dispersion provided by each grating when mounted on the 235mm camera. The RED+2 is mounted with its 4096 pixel axis along the wavelength direction, giving maximum use of the beam width leaving the cameras. However the camera optics severely vignette the outer regions of the dispersed light beam such that approximately only 2070 of the CCD pixels are clear and unvignetted. The attenuation runs rises steeply at each end of the spectra. The unvignetted portion is roughly from pixel number 800 to 3200 in the spectral direction. Here is an example plot of a lamp flat on the 235mm camera with RED+2 CCD.  

The 235mm camera with RED+2 CCD provides a spatial scale of 0.44 arcsec/pixel. The maximum unvignetted slit-length usable with IDS is 3.3 arcmin, corresponding to some 450 detector pixels for RED+2.

Note that the spatial (=along the slit) profile degrades toward the upper and bottom parts of the CCD, giving the impression that in these regions the star image is out-of-focus (most evident in the vignetted regions where a stellar profiles becomes double-peaked). This is a feature due to the IDS optics, in particular the CCD corrector lens, that was not designed for large format detectors like the RED+2 CCD.

RED+2 chip suffers from fringing in the red part of the spectrum, which limits its usefulness in this region despite their continued good QE up to 8000Å. Here you have an illustrative flat field spectra showing fringing in the redmost part (around 0.9 microns), and here you have an example showing the fringing modulation along the whole RED+2 CCD with R300V gratings covering up to 10,000A. The level of fringing is less than 2% in all interval, with an average of about 1%. There are a few cosmetic defects on the surface of the chip, but nothing particularly severe. The diffusion of charges between pixels during integrations causes a degrading of the spatial and spectral resolution. For a long-slit spectrograph like IDS, with the INT mean seeing around 1".0-1".5, spatial degradation is not a significant worry with the pixel size of the RED+2, but it is a consideration in the spectral direction. For a back illuminated CCD this charge diffusion (often referred to as the Modulation Transfer Function; MTF) becomes progressively worse for shorter wavelength incident light. For example, using a slit-width projecting to 2 pixels on the detector results in a FWHM measured of 2.4 pixels (measured at ~4000Å) when the spectrograph is at best focus. Similarly a slit-width projecting to 4 detector pixels will produce a FWHM of ~4.4 pixels (again at ~4000Å). This effect becomes less severe towards redder wavelengths and is negligible at around 6000Å.