I want to calculate the number of participants I need in order to get a power of 0.95, when replicating an effect. The effect size of this effect is not reported in the previous study, which is why I want to calculate it from the F value and the degrees of freedom. The ANOVA is a repeated-measures ANOVA with within-group manipulation (two conditions). 
Is the following formula adequate to calculate partial eta squared?

$\eta^2_p = \frac{F \cdot df_{\text{effect}}}{F\cdot df_{\text{effect}}+df_{\text{error}}}$
========================================================================