Detectors

Five modes of on-chip binning are available in the readout of the data from the CCDs. The readout time for each binning mode is given in Table . Note that the saturation level described in Section is applied to the summation of the counts for binned pixels. Therefore the maximum S/N ratio achieved by a single exposure with binning is lower than that without binning. This point should be considered in observations which require very high S/N data for bright objects.

Table 5: CCD readout time

Setup for binning (spatial×dispersion)	Total dead time for one exposure (sec.)
1×1	~86
2×1	~60
2×2	~44
2×4	~36
4×4	~33