
 mextract (filename) (value) [-g / -a Ncol]

 extracts a vector from the photometry database.  The name also
 specifies the type of data extracted (and is case insensitive).  Only
 certain names may be used.

 The possible values are:
 ra, dec, mag, dmag, Mcal, Mrel, source, time, dR, dD


 Note: this routine extracts the individual measurements.
