pep_bias = 1000.
eit_bias = 400.
 pep_bias = 0.
 eit_bias = 0.

tv,bytscl(pepmm,3000,20000),-120,0
tv,bytscl(eitim,200,5000),400,0

bpep = pepmm - pep_bias
bpep = bpep > 0.
tv,bytscl(bpep,0,20000)

beit = eitim - eit_bias
beit = beit > 0.
tv,bytscl(beit,0,6000)


forever = 1
while forever do begin
	tv,bytscl(bpep,0,15000)

	cursor, x, y,/NORMAL     &     if ( !ERR eq 4 ) then forever = 0

	tv,bytscl(beit,0,5000)

	cursor, x, y,/NORMAL     &     if ( !ERR eq 4 ) then forever = 0
endwhile




;  find overlap where two images are non-zero

whr = where(bpep gt 0 and beit gt 0)
ratio = pepmm & ratio(*,*) = 0.
ratio(whr) = bpep(whr)/beit(whr)

tv,bytscl(ratio, 1.,9.)

;; ratio(whr) = beit(whr)  /  bpep(whr)

;; tv,bytscl(ratio, 0. , 1.)


end