###Exposure Time Calculator###

     * What are the minimum and maximum length of an exposure with each
     detector? 
     Exposure times for all 3 detectors must be integer multiples of
     0.1 sec.
     ACCUM Mode:
     For HRC and SBC, the legal range is 0.1 to 3600.0 sec.
     For WFC, the legal range is 0.5 to 3600.0 sec, except
     that 0.6 sec is not allowed.
     (For WFC and HRC, CAL & ENG proposals may use the BIAS target, 
     in which case 0.0 sec must be specified.)
     ACQ Mode:
     For HRC Target Acquisitions, the legal range is 0.1 to 300.0 sec.
     (Up to 3600.0 is allowed for CAL & ENG proposals.)