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The CHAMELEON collection of scripts as part of
is used to read,
edit, average, and calibrate output (“point data”) produced from raw
fringe data by a standalone C program, CONSTRICTOR. The scripts are
run interactively in the IDL environment, with the data stored in IDL
variables and therefore available at the command level. Beginning with
version 8, a pipeline has been implemented which produces averaged and
calibrated data.
Data reduction and analysis are two steps separated by the average procedure. In the classic NPOI 3-way reduction, the squared visibility, delay, background and photonrate data are edited, then averaged into scans. For astrometry, the emphasis is on the dispersion correction of the delay point data before the averaging step. Calibration of the scan-averaged visibilities is based on unresolved or nearly unresolved calibrator stars, whereas the astrometric calibration is based on the application of constant term and pivot motion metrology data delivered by INCHWORM. A new feature of the 6-way data reduction is the photometric and bias calibrations derived from the averaged data, but used in a second averaging step in order for them to be applied.
Following the Introduction, a Quick Guide will lead you through a sample session. Basic widget procedures is a more comprehensive description of how to reduce data using the GUI (Graphical User Interface). Command line procedures lists some of the useful routines callable at the IDL prompt.