FOCAS readout modes

FOCAS has a number of readout modes for on-chip binning of data. This can be useful to significantly improve the signal-to-noise ratio for faint objects, or where resolution (spatial and/or spectral) is not essential.

Note: Since 2003 September, longer readout time is required to reduce read noise.

Binning
(spatial x spectral)
Readout
time (s)
Image size
1 x 1 166 2047 x 4095
2 x 1 85
1023 x 4095
3 x 1 61
683 x 4095
4 x 1 49
512 x 4095
2 x 2 52
1023 x 2047
3 x 2 37
683 x 2047
4 x 2 29
512 x 2047
2 x 3
36
1023 x 1365
3 x 3
26
683 x 1365
4 x 3
20
512 x 1365
3 x 4
19
683 x  1023
4 x 4
15
512 x 1023

Some partial readout modes with either 1 x 1 or 2 x 2 binning are available for quicker target acquisition on slits.



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