lan_dyn_spect_stream::get_back_change

Source: stream/dyn_spect/Lan/lan_dyn_spect_stream__get_back_change.pro

 lan_dyn_spect_stream::get_back_change
        Return the JD of the change of background level.

 Usage:
        strref -> get_back_change()

 History:
        Original: 22/3/00; SJT