; Given type (string, e.g, "O"), subtype (float, e.g. 3)
; and class (integer), return B-V from
; AQ 4th ed
;

function aq_bv, type, subtype, class
  functionname = 'aq_bv'
  CASE class OF
    5: begin ; Main sequence
	    CASE type OF
		'O': begin 
			x = [5,9] & y = [-0.33,-0.31]
		     end
		'B': begin 
			x = [0,2,5,8] & y = [-0.30,-0.24,-0.17,-0.11]
		     end
		'A': begin 
			x = [0,2,5] & y = [-0.02,0.05,0.15]
		     end
		'F': begin 
			x = [0,2,5,8] & y = [0.30,0.35,0.44,0.52]
		     end
		'G': begin 
			x = [0,2,5,8] & y = [0.58,0.63,0.68,0.74]
		     end
		'K': begin 
			x = [0,2,5] & y = [0.81,0.91,1.15]
		     end
		'M': begin 
			x = [0,2,5] & y = [1.40,1.49,1.64]
		     end
	  ENDCASE
       end
    3: begin ; giants. Teff for O-F are from xx
	    CASE type OF
		'G': begin 
			x = [5,8] & y = [0.86,0.94]
		     end
		'K': begin 
			x = [0,2,5] & y = [1.00,1.16,1.50]
		     end
		'M': begin 
			x = [0,2,5] & y = [1.56,1.60,1.63]
		     end
		 ELSE: begin ; out of bounds! 
		    print, 'aq_teff: spectral type out of bounds'
		    return,-100
		    end
	  ENDCASE
       end
    1: begin ; super giants. Teff for O-B2 are from xx
	    CASE type OF
		'B': begin 
 			   x = [2,5,8] 
			   y = [-0.17,-0.10,-0.03]
		     end
		'A': begin 
			x = [0,2,5] & y = [-0.01,0.03,0.09]
		     end
		'F': begin 
			x = [0,2,5,8] & y = [0.17,0.23,0.32,0.56]
		     end
		'G': begin 
			x = [0,2,5,8] & y = [0.76,0.87,1.02,1.14]
		     end
		'K': begin 
			x = [0,2,5] & y = [1.25,1.36,1.60]
		     end
		'M': begin 
			x = [0,2,5] & y = [1.67,1.71,1.80]
		     end
		  ELSE: begin ; out of bounds! 
		    print, 'aq_teff: spectral type out of bounds'
		    return, -100
		    end
	  ENDCASE
       end
  ELSE: begin ; out of bounds! 
    print, functionname+': spectral type out of bounds'
    return, -100
    end
  ENDCASE

  res = poly_fit(x, y, 1) 
  color = poly(subtype,res)
  return, color
end