10.
已知椭圆\(C\):\( \dfrac {x^{2}}{a^{2}}+ \dfrac {y^{2}}{b^{2}}=1(a > b > 0)\)的长轴长是短轴长的\( \dfrac {3 \sqrt {5}}{5}\)倍,\(A\)是椭圆\(C\)的左顶点,\(F\)是椭圆\(C\)的右焦点,点\(M(x_{0},y_{0})(x_{0} > 0,y_{0} > 0)\),\(N\)都在椭圆\(C\)上.
\((\)Ⅰ\()\)若点\(D(-1, \dfrac {2 \sqrt {10}}{3})\)在椭圆\(C\)上,求\(|NF|\)的最大值;
\((\)Ⅱ\()\)若\( \overrightarrow{OM}=2 \overrightarrow{AN}(O\)为坐标原点\()\),求直线\(AN\)的斜率.