Exposure meter

To protect the new FIES exposure meter a device has been designed to monitor the light level near the meter and when it exceeded a certain level (well within the limits of the photo-multiplier), it will cut the power and send a signal for the software to read, indicating what has happened.

An exposure-meter count calculator was developed, see

      http://www.not.iac.es/instruments/fies/emcc/ ,
that calculates for a given fiber/resolution (and as a function of the ``color'' of the target) the require number of counts from the exposure-meter to reach a specific signal-to-noise. The FIES obstructions related to the exposure meter were updated and improved.

Following a request from one of the observers, we plan for exposures that use the exposure-meter to use the measurements from the meter to calculate an intensity-weighted time of mid-exposure and add this to the FITS header.

Thomas Augusteijn 2010-02-09