Getting Information about Images

To get the observation time
IDL> print,fmt_tim(index) $<$CR$>$
To get the image frequency
IDL> print,norh_gt_freq(index) $<$CR$>$
To get the circular polarization information
IDL> print,norh_gt_polariz(index) $<$CR$>$
To get the position of the image center in the coordinate in which the origin is the solar disk center and the unit is arcsec
IDL> print,norh_gt_imgcen(index) $<$CR$>$
To get the roll of the image (usually zero)
IDL> print,norh_cen(index,roll=roll) $<$CR$>$
To get the exposure duration of the image
IDL> print,norh_gt_expdur(index) $<$CR$>$