pro utslt 
  if utvert.utvert_type eq 'slt' then begin
      uthrs=mtime[0,j]*24.+mtime[1,j]+mtime[2,j]/60.
    if minutes le 24.*60. then begin
      slthrs=mtime[0,j]*24.+utvert.sslt
    endif else begin
      slthrs=utvert.sslt*24.
    endelse
    newlon=(slthrs-uthrs)*15.
    ilon = ixfind_nearest(lons,newlon)
  endif
end