function check_struct, image_List, Magf, sim, simsc, ALL_MAGS=all_mags

;Frank Varosi NASA/GSFC 1989.

	if N_tags( image_List ) LE 0 then return,(0)

	if  N_params() GE 2 then $
		Magf = check_Mag_Fact( image_List, sim, simsc, ALL=all_mags )

return, N_elements( image_List )
end