pro j15sum_dif,imn=imn,imset=imset,img=img
;
  if n_elements(imn) eq 0 then imn = '3200'
  if n_elements(imset) eq 0 then imset = 'jan15_'
  if n_elements(img) eq 0 then img = 2384
  imgs = img
  imgq = 15
;
; directory from where to get images
;
namex = '[bjackson.lasco.datr]'
;
; directory into which to place difference images 
;
name='[bjackson.lasco.datns]'
; 
; image/s to use as base
; 
  starless = fltarr(5,5)
  nami0  = '2308'
  nami1  = '2312'
  nami2  = '2316'
  nami3  = '2320'
  fini1 = '.fts'
  fini2 = '.dif'
  for ii=0,3 do begin
  if ii eq 0 then nami = nami0
  if ii eq 1 then nami = nami1
  if ii eq 2 then nami = nami2
  if ii eq 3 then nami = nami3
  nameb = namex+imn+nami+fini1
  base1 = readfits(nameb,hdrb)
  if ii eq 0 then begin
	base00 = base1
	base00(*,*) = 0.0
        base0 = base00
  endif
;
; Remove stars from the base image by finding the minimum within an area
;
  for i=2,512-3 do begin
    for j=2,256-3 do begin
      starless=base1(i-2:i+2,j-2:j+2)
      minstarless = min(starless)
      base00(i,j) = minstarless
    endfor
  endfor
;
; Sum 4 base images together to remove any small-scale heliospheric density 
; structure. (The structure will have moved over the time of the average.)
;
  base0 = base0 + base00
  endfor
  base0(*,*) = base0(*,*)/4.0
start:
;
; Image to use name.
;
  namei = namex+imn+strcompress(img,/rem)+fini1
;
; Difference result name
;
  namen = name+imset+strcompress(img,/rem)+fini2
;
  second  = readfits(namei,hdr)
  second = second - base0
;
 writefits, namen, second, hdr
 tv, second
 img = img + 4
 if img gt imgs + imgq*4 then goto, end1
;
 goto, start
;
 end1:
;
end