Summer is over and fall has started. Today's fractal  remembers the green which
 has not completely faded. Both gif and re-sampled jpg posted at the
usual http://maxitersfractalfollies.blogspot.com As promised yesterday's image
 has been re-sampled and posted.


Green Filaments  { ; fract470.gif
                     ; blank
                     ; calctime   0:01:44.75
                     ; created Oct 14, 2010
                     ;  Fractint Version 2004 Patchlevel 9
  reset=2004 type=formula formulafile=kerrym.frm
  formulaname=field3_jul center-mag=0.0829957/0.59665/2.9036
  params=0.375/0.5/100000000/4 float=y maxiter=1500 inside=0
  decomp=256
  colors=0100200300400500700800900A00B00D00E00F00G00H00J00K00L00M00N00P00Q\
  00R00S00T00V00W00X00Y00Z00`00a00b00c00d00f00g00h00i00k00k01k02k03l04l05l\
  05m06m07m08n09n0An0Bo0Bo0Co0Dp0Ep0Fp0Gp0Hq0Hq0Iq0Jr0Kr0Lr0Ms0Ns0Ns0Ot0Pt\
  0Qt0Ru0Su0Tu0Tu0Uv0Vv0Wv0Xw0Yw0Zw0Zx0_x0`x0ay0by0cy0dz1dz1ez1ez1fz2fz2gz\
  2gz2hz3hz3iz3iz3jz4jz4kz4kz4lz5mz5mz5nz5nz6oz6oz6pz6pz7qz7qz7rz7rz8sz8sz\
  8tz8uz9uz9uz9tz9tz9tz9sz9sz8sz8rz8rz8rz8qz8qz7qz7pz7pz7oz7oz7oz6nz6nz6nz\
  6mz6mz6mz5lz5lz5lz5kz5kz5kz4jz4jz4iz4iz4iz4hz3hz3hz3gz3gz3gz3fz2fz2fz2ez\
  2ez2dz1dz1cz1bz1ay1`y1_y1_x1Zx1Yx1Xw1Ww1Vw1Uv1Uv1Tv1Su1Ru1Qu1Pt1Ot1Ot1Nt\
  1Ms1Ls1Ks1Jr1Ir1Ir1Hq1Gq1Fq1Ep1Dp1Cp1Co1Bo1Ao19n18n17n16m06l06k06j06i06h\
  06g06f05e05d05c05b05a05`05_05Z04Y04X04W04V04U04T04S04R03P03O03N03M03L03K\
  03J03I02H02G02F02E02D02C02B02A0190180170160150140130010
  }
frm:field3_jul { ; Kerry Mitchell 20jan98
        ;
        ; Colors Julia sets by nearest approach to
        ;   period 3 field lines
        ;
        ; use decomp=256
        ; p1 = Julia parameter
        ; real(p2) = bailout (try 1e12)
        ; imag(p2) = number of field line to use:
        ;   0, 1, 2, 3, 4, 5, 6, 7
        ; 3 iterations per pixel
        ; variable zc used for calculation, z for coloring
        ;
        zc=pixel, c=p1, maxr=real(p2), minr=maxr, iter=1
        fieldangle=tan(imag(p2)*2*pi/7):
        ;
        ; iteration
        ;   compare tangent of polar angle with desired
        ;   field line angle, update minimum if needed
        ;
        iter=iter+3, zc=sqr(zc)+c, zc=sqr(zc)+c, zc=sqr(zc)+c
        rzc=|zc|, tanangle=imag(zc)/real(zc),
        r=cabs(fieldangle-tanangle)
        if (r<minr)
          minr=r
          end if
        ;
        ; bailout
        ;   set "iteration done" flag (iter=-1)
        ;   use log of minimum difference of angles as
        ;     decomposition angle
        ;
        if ((rzc>maxr)||(iter>=maxit))
          iter=-1
          angle=log(minr)
          z=cos(angle)+flip(sin(angle))
          end if
        iter>0
        }
Roger Alexander