For detecting Siegel disc around fixed point in a plot of the Julia set of f one can use average discrete velocity of orbit.
http://upload.wikimedia.org/wikipedia/commons/e/ea/Golden_Mean_Quadratic_Siegel_Disc_Speed.png
It is decribed here
http://commons.wikimedia.org/wiki/File%3AGolden_Mean_Quadratic_Siegel_Disc_Speed.png
I have learned this method from Chris King
http://www.dhushara.com/DarkHeart/DarkHeart.htm
To highligght boundaries of Siegel disk components in a plot of the Julia set of f one can use this method :
It works for cases when critical point is on the boundary of Siegel disc component.
See : Building blocks for Quadratic Julia sets by : Joachim Grispolakis, John C. Mayer and Lex G. Oversteegen Journal: Trans. Amer. Math. Soc. 351 (1999), 1171-1201
HTH
Adam
( I can't use image tags )
