.在直角坐标系\(xOy\)中,直线\(l\)\(:\)\(y=t\)\((\)\(t\)\(\neq 0)\)交\(y\)轴于点\(M\),交抛物线\(C\)\(:\)\(y\)\({\,\!}^{2}\)\(=\)\(2\)\(px\)\((\)\(p > \)\(0)\)于点\(P\),\(M\)关于点\(P\)的对称点为\(N\),连接\(ON\)并延长交\(C\)于点\(H\).
\((1)\)求\( \dfrac{\left|OH\right|}{\left|ON\right|} ;\)
\((2)\)除\(H\)以外,直线\(MH\)与\(C\)是否有其他公共点\(?\)说明理由.