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This form allows you to calculate ULTRASPEC frame rates to an accuracy
of a few per cent. The frame rate is the inverse of the sum of the
exposure time and the dead time and depends on a number of parameters,
including the number, size, position and binning factors of the
windows, the EMCCD readout speed and whether the normal or avalanche output
is being used, all of which are variables in the ULTRASPEC user
interface. The exposure time of an ULTRASPEC observation is not as
straight-forward a concept as it is for conventional CCD cameras, as
it is composed of the time it takes to empty the storage area plus the
user-defined exposure delay. The only situation in which the
exposure delay is equal to the exposure time is when the
clear mode of ULTRASPEC is being used. For further details,
please consult Appendix A of Dhillon et al. (2007, MNRAS, 378, 825) and/or the fortran source code.
Note that for drift mode, two windows must be used. The ystart and ysize parameters of the two windows must be the same. Note also that the calculator below automatically deals with the window x-position conversions required when switching between normal and avalanche outputs. | |
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