pro fits_cut,Directory=Directory,letter=letter,threshold=threshold

If (not keyword_set(Directory)) then Directory='/a/pippin01/Volumes/u08/lsst/CPanalysis/2005-05-10/ShackHartman/'
If (not keyword_set(letter)) then letter='a'
If (not keyword_set(threshold)) then threshold=250

for file_number=1, 99 do begin

if file_number lt 10 then begin
                fits_file_name=Directory+'hr5132'+letter+'_'+$
                string(file_number,format='(I1)')+'_raw.fits'
        endif
        if file_number ge 10 and file_number lt 100 then begin
                fits_file_name=Directory+'hr5132'+letter+'_'+$
                string(file_number,format='(I2)')+'_raw.fits'
        endif
        if file_number ge 100 and file_number lt 1000 then begin
                fits_file_name=Directory+'hr5132'+letter+'_'+$
                string(file_number,format='(I3)')+'_raw.fits'                                                                                               
        endif

	fits_read,fits_file_name,image,header

	image(where(image lt threshold))=0

	writefits,fits_file_name+'zeroed.fits',image

endfor

end