;+
; NAME:
;  rho_of_fg
; PURPOSE: (one line)
;  shadow radius given a lc table structure and f0, g0
; DESCRIPTION:
;  shadow radius given a lc table structure and f0, g0
; CATEGORY:
;  oc
; CALLING SEQUENCE:
;  rho=rho_of_fg(table, f0, g0, fos, gos)
; INPUTS:
;  f0 - offset in east position
;  g0 - offset in north position
; OPTIONAL INPUT PARAMETERS:
;  none
; KEYWORD INPUT PARAMETERS:
;  none
; KEYWORD OUTPUT PARAMETERS:
;  none
; OUTPUTS:
;  rho_km - shadow radius in km
; OPTIONAL OUTPUTS:
;  f_os - F (eastward) position of observer - target
;  g_os - G (northward) position of observer - target
; PROCEDURE:
;  the coordinates fgh are defined so that
;  f is sky east
;  g is sky north
;  h is the vector from the observer to the star
;
;  f0 and g0 are defined as in Elliot et al 1993 ("Amanda's Saturn paper"):
;
;  table.f_nom and table.g_nom from our lc_*fits ascii table files
;  which save the f and g calcuated from NAIF as target - observer
;
;  f_obs-targ = -f_nom_targ-obs - f0
; 
;  g_obs-targ = -g_nom_targ-obs - g0
;  
; tab = fits table of occultation with f_nom, g_nom 
; defined as TARGET CENTER - OBSERVER in fgh coordinates
;
; MODIFICATION HISTORY:
;-

function rho_of_fg, tab, f0, g0, f_os, g_os

	f_os = - tab.f_nom - f0
	g_os = - tab.g_nom - g0
	return, sqrt(f_os^2 + g_os^2)

end