The 'trace-width-threshold' is provided for cases when the S/N of
the frame being examined to locate the orders is very low.
The threshold is the degree to which off-trace pixels must fall below
the pixel at trace centre (in the spatial direction) in order to be
considered as 'off-order'. I.e., the trace width is estimated
by stepping pixel-by-pixel above and below the trace until the
intensity falls below (1.0 - TUNE_TWTHR) x
The default value is 0.95 (95%).
ECHOMOP-Echelle Data Reduction Package
Starlink User Note 152
2003 July 14
Copyright © 2003 Council for the Central Laboratory of the Research Councils