ULTRASPEC frame-rate calculator

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.

exposure delay  msecs
output  normal      avalanche 
readout speed  slow      medium      fast     
drift mode  disabled      enabled 
clear mode  disabled      enabled 
binning in x, y  
window 1 - xstart, xsize, ystart, ysize
(1,1056,1,1072 for full frame)
window 2 - xstart, xsize, ystart, ysize
(0,0,0,0 to disable window)
window 3 - xstart, xsize, ystart, ysize
(0,0,0,0 to disable window)
window 4 - xstart, xsize, ystart, ysize
(0,0,0,0 to disable window)